diff --git a/README.md b/README.md
index 04e3774..1d73f59 100644
--- a/README.md
+++ b/README.md
@@ -29,9 +29,10 @@ first time.
 System Requirements
 -------------------
 
-This project depends on Python 2.7 and the Mercurial >= 4.6
-package. If Python is not installed, install it before proceeding. The
-Mercurial package can be installed with `pip install mercurial`.
+This project depends on Python 2.7 or 3.5+, and the Mercurial >= 4.6
+package (>= 5.2, if Python 3.5+). If Python is not installed, install
+it before proceeding. TheMercurial package can be installed with
+`pip install mercurial`.
 
 On windows the bash that comes with "Git for Windows" is known to work
 well.
diff --git a/hg-fast-export.py b/hg-fast-export.py
index c005836..76d4679 100755
--- a/hg-fast-export.py
+++ b/hg-fast-export.py
@@ -11,9 +11,13 @@ from optparse import OptionParser
 import re
 import sys
 import os
+from binascii import hexlify
 import pluginloader
+PY2 = sys.version_info.major == 2
+if PY2:
+  str = unicode
 
-if sys.platform == "win32":
+if PY2 and sys.platform == "win32":
   # On Windows, sys.stdout is initially opened in text mode, which means that
   # when a LF (\n) character is written to sys.stdout, it will be converted
   # into CRLF (\r\n).  That makes git blow up, so use this platform-specific
@@ -22,7 +26,7 @@ if sys.platform == "win32":
   msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
 
 # silly regex to catch Signed-off-by lines in log message
-sob_re=re.compile('^Signed-[Oo]ff-[Bb]y: (.+)$')
+sob_re=re.compile(b'^Signed-[Oo]ff-[Bb]y: (.+)$')
 # insert 'checkpoint' command after this many commits or none at all if 0
 cfg_checkpoint_count=0
 # write some progress message every this many file contents written
@@ -35,30 +39,33 @@ submodule_mappings=None
 # author/branch/tag names.
 auto_sanitize = None
 
+stdout_buffer = sys.stdout if PY2 else sys.stdout.buffer
+
 def gitmode(flags):
-  return 'l' in flags and '120000' or 'x' in flags and '100755' or '100644'
+  return b'l' in flags and b'120000' or b'x' in flags and b'100755' or b'100644'
 
-def wr_no_nl(msg=''):
+def wr_no_nl(msg=b''):
+  assert isinstance(msg, bytes)
   if msg:
-    sys.stdout.write(msg)
+    stdout_buffer.write(msg)
 
-def wr(msg=''):
+def wr(msg=b''):
   wr_no_nl(msg)
-  sys.stdout.write('\n')
+  stdout_buffer.write(b'\n')
   #map(lambda x: sys.stderr.write('\t[%s]\n' % x),msg.split('\n'))
 
 def checkpoint(count):
   count=count+1
   if cfg_checkpoint_count>0 and count%cfg_checkpoint_count==0:
     sys.stderr.write("Checkpoint after %d commits\n" % count)
-    wr('checkpoint')
+    wr(b'checkpoint')
     wr()
   return count
 
 def revnum_to_revref(rev, old_marks):
   """Convert an hg revnum to a git-fast-import rev reference (an SHA1
   or a mark)"""
-  return old_marks.get(rev) or ':%d' % (rev+1)
+  return old_marks.get(rev) or b':%d' % (rev+1)
 
 def file_mismatch(f1,f2):
   """See if two revisions of a file are not equal."""
@@ -87,7 +94,7 @@ def get_filechanges(repo,revision,parents,mleft):
   l,c,r=[],[],[]
   for p in parents:
     if p<0: continue
-    mright=revsymbol(repo,str(p)).manifest()
+    mright=revsymbol(repo,b"%d" %p).manifest()
     l,c,r=split_dict(mleft,mright,l,c,r)
   l.sort()
   c.sort()
@@ -110,7 +117,7 @@ def get_author(logmessage,committer,authors):
   "Signed-off-by: foo" and thus matching our detection regex. Prevent
   that."""
 
-  loglines=logmessage.split('\n')
+  loglines=logmessage.split(b'\n')
   i=len(loglines)
   # from tail walk to top skipping empty lines
   while i>=0:
@@ -138,23 +145,24 @@ def remove_gitmodules(ctx):
   # be to only remove the submodules of the first parent.
   for parent_ctx in ctx.parents():
     for submodule in parent_ctx.substate.keys():
-      wr('D %s' % submodule)
-  wr('D .gitmodules')
+      wr(b'D %s' % submodule)
+  wr(b'D .gitmodules')
 
 def refresh_git_submodule(name,subrepo_info):
-  wr('M 160000 %s %s' % (subrepo_info[1],name))
-  sys.stderr.write("Adding/updating submodule %s, revision %s\n"
-                   % (name,subrepo_info[1]))
-  return '[submodule "%s"]\n\tpath = %s\n\turl = %s\n' % (name,name,
-    subrepo_info[0])
+  wr(b'M 160000 %s %s' % (subrepo_info[1],name))
+  sys.stderr.write(
+    "Adding/updating submodule %s, revision %s\n"
+    % (name.decode('utf8'), subrepo_info[1].decode('utf8'))
+  )
+  return b'[submodule "%s"]\n\tpath = %s\n\turl = %s\n' % (name, name, subrepo_info[0])
 
 def refresh_hg_submodule(name,subrepo_info):
-  gitRepoLocation=submodule_mappings[name] + "/.git"
+  gitRepoLocation=submodule_mappings[name] + b"/.git"
 
   # Populate the cache to map mercurial revision to git revision
   if not name in subrepo_cache:
-    subrepo_cache[name]=(load_cache(gitRepoLocation+"/hg2git-mapping"),
-                         load_cache(gitRepoLocation+"/hg2git-marks",
+    subrepo_cache[name]=(load_cache(gitRepoLocation+b"/hg2git-mapping"),
+                         load_cache(gitRepoLocation+b"/hg2git-marks",
                                     lambda s: int(s)-1))
 
   (mapping_cache,marks_cache)=subrepo_cache[name]
@@ -162,30 +170,38 @@ def refresh_hg_submodule(name,subrepo_info):
   if subrepo_hash in mapping_cache:
     revnum=mapping_cache[subrepo_hash]
     gitSha=marks_cache[int(revnum)]
-    wr('M 160000 %s %s' % (gitSha,name))
-    sys.stderr.write("Adding/updating submodule %s, revision %s->%s\n"
-                     % (name,subrepo_hash,gitSha))
-    return '[submodule "%s"]\n\tpath = %s\n\turl = %s\n' % (name,name,
+    wr(b'M 160000 %s %s' % (gitSha,name))
+    sys.stderr.write(
+      "Adding/updating submodule %s, revision %s->%s\n"
+      % (name.decode('utf8'), subrepo_hash.decode('utf8'), gitSha.decode('utf8'))
+    )
+    return b'[submodule "%s"]\n\tpath = %s\n\turl = %s\n' % (name,name,
       submodule_mappings[name])
   else:
-    sys.stderr.write("Warning: Could not find hg revision %s for %s in git %s\n" %
-      (subrepo_hash,name,gitRepoLocation))
-    return ''
+    sys.stderr.write(
+      "Warning: Could not find hg revision %s for %s in git %s\n"
+      % (
+        subrepo_hash.decode('utf8'),
+        name.decode('utf8'),
+        gitRepoLocation.decode('utf8'),
+      )
+    )
+    return b''
 
 def refresh_gitmodules(ctx):
   """Updates list of ctx submodules according to .hgsubstate file"""
   remove_gitmodules(ctx)
-  gitmodules=""
+  gitmodules=b""
   # Create the .gitmodules file and all submodules
   for name,subrepo_info in ctx.substate.items():
-    if subrepo_info[2]=='git':
+    if subrepo_info[2]==b'git':
       gitmodules+=refresh_git_submodule(name,subrepo_info)
     elif submodule_mappings and name in submodule_mappings:
       gitmodules+=refresh_hg_submodule(name,subrepo_info)
 
   if len(gitmodules):
-    wr('M 100644 inline .gitmodules')
-    wr('data %d' % (len(gitmodules)+1))
+    wr(b'M 100644 inline .gitmodules')
+    wr(b'data %d' % (len(gitmodules)+1))
     wr(gitmodules)
 
 def export_file_contents(ctx,manifest,files,hgtags,encoding='',plugins={}):
@@ -193,19 +209,21 @@ def export_file_contents(ctx,manifest,files,hgtags,encoding='',plugins={}):
   max=len(files)
   is_submodules_refreshed=False
   for file in files:
-    if not is_submodules_refreshed and (file=='.hgsub' or file=='.hgsubstate'):
+    if not is_submodules_refreshed and (file==b'.hgsub' or file==b'.hgsubstate'):
       is_submodules_refreshed=True
       refresh_gitmodules(ctx)
     # Skip .hgtags files. They only get us in trouble.
-    if not hgtags and file == ".hgtags":
-      sys.stderr.write('Skip %s\n' % (file))
+    if not hgtags and file == b".hgtags":
+      sys.stderr.write('Skip %s\n' % file.decode('utf8'))
       continue
     if encoding:
       filename=file.decode(encoding).encode('utf8')
     else:
       filename=file
-    if '.git' in filename.split(os.path.sep):
-      sys.stderr.write('Ignoring file %s which cannot be tracked by git\n' % filename)
+    if b'.git' in filename.split(os.path.sep.encode()):
+      sys.stderr.write(
+          'Ignoring file %s which cannot be tracked by git\n' % filename.decode('utf8')
+      )
       continue
     file_ctx=ctx.filectx(file)
     d=file_ctx.data()
@@ -218,9 +236,9 @@ def export_file_contents(ctx,manifest,files,hgtags,encoding='',plugins={}):
       filename=file_data['filename']
       file_ctx=file_data['file_ctx']
 
-    wr('M %s inline %s' % (gitmode(manifest.flags(file)),
+    wr(b'M %s inline %s' % (gitmode(manifest.flags(file)),
                            strip_leading_slash(filename)))
-    wr('data %d' % len(d)) # had some trouble with size()
+    wr(b'data %d' % len(d)) # had some trouble with size()
     wr(d)
     count+=1
     if count%cfg_export_boundary==0:
@@ -246,25 +264,28 @@ def sanitize_name(name,what="branch", mapping={}):
 
   def dot(name):
     if not name: return name
-    if name[0] == '.': return '_'+name[1:]
+    if name[0:1] == b'.': return b'_'+name[1:]
     return name
 
   if not auto_sanitize:
     return mapping.get(name,name)
   n=mapping.get(name,name)
-  p=re.compile('([[ ~^:?\\\\*]|\.\.)')
-  n=p.sub('_', n)
-  if n[-1] in ('/', '.'): n=n[:-1]+'_'
-  n='/'.join(map(dot,n.split('/')))
-  p=re.compile('_+')
-  n=p.sub('_', n)
+  p=re.compile(b'([[ ~^:?\\\\*]|\.\.)')
+  n=p.sub(b'_', n)
+  if n[-1:] in (b'/', b'.'): n=n[:-1]+b'_'
+  n=b'/'.join([dot(s) for s in n.split(b'/')])
+  p=re.compile(b'_+')
+  n=p.sub(b'_', n)
 
   if n!=name:
-    sys.stderr.write('Warning: sanitized %s [%s] to [%s]\n' % (what,name,n))
+    sys.stderr.write(
+        'Warning: sanitized %s [%s] to [%s]\n'
+        % (what, name.decode('utf8'), n.decode('utf8'))
+    )
   return n
 
 def strip_leading_slash(filename):
-  if filename[0] == '/':
+  if filename[0:1] == b'/':
     return filename[1:]
   return filename
 
@@ -272,7 +293,7 @@ def export_commit(ui,repo,revision,old_marks,max,count,authors,
                   branchesmap,sob,brmap,hgtags,encoding='',fn_encoding='',
                   plugins={}):
   def get_branchname(name):
-    if brmap.has_key(name):
+    if name in brmap:
       return brmap[name]
     n=sanitize_name(name, "branch", branchesmap)
     brmap[name]=n
@@ -297,18 +318,18 @@ def export_commit(ui,repo,revision,old_marks,max,count,authors,
     desc = commit_data['desc']
 
   if len(parents)==0 and revision != 0:
-    wr('reset refs/heads/%s' % branch)
+    wr(b'reset refs/heads/%s' % branch)
 
-  wr('commit refs/heads/%s' % branch)
-  wr('mark :%d' % (revision+1))
+  wr(b'commit refs/heads/%s' % branch)
+  wr(b'mark :%d' % (revision+1))
   if sob:
-    wr('author %s %d %s' % (author,time,timezone))
-  wr('committer %s %d %s' % (user,time,timezone))
-  wr('data %d' % (len(desc)+1)) # wtf?
+    wr(b'author %s %d %s' % (author,time,timezone))
+  wr(b'committer %s %d %s' % (user,time,timezone))
+  wr(b'data %d' % (len(desc)+1)) # wtf?
   wr(desc)
   wr()
 
-  ctx=revsymbol(repo,str(revision))
+  ctx=revsymbol(repo, b"%d" % revision)
   man=ctx.manifest()
   added,changed,removed,type=[],[],[],''
 
@@ -318,7 +339,7 @@ def export_commit(ui,repo,revision,old_marks,max,count,authors,
     added.sort()
     type='full'
   else:
-    wr('from %s' % revnum_to_revref(parents[0], old_marks))
+    wr(b'from %s' % revnum_to_revref(parents[0], old_marks))
     if len(parents) == 1:
       # later non-merge revision: feed in changed manifest
       # if we have exactly one parent, just take the changes from the
@@ -327,7 +348,7 @@ def export_commit(ui,repo,revision,old_marks,max,count,authors,
       added,changed,removed=f.added,f.modified,f.removed
       type='simple delta'
     else: # a merge with two parents
-      wr('merge %s' % revnum_to_revref(parents[1], old_marks))
+      wr(b'merge %s' % revnum_to_revref(parents[1], old_marks))
       # later merge revision: feed in changed manifest
       # for many files comparing checksums is expensive so only do it for
       # merges where we really need it due to hg's revlog logic
@@ -335,15 +356,15 @@ def export_commit(ui,repo,revision,old_marks,max,count,authors,
       type='thorough delta'
 
   sys.stderr.write('%s: Exporting %s revision %d/%d with %d/%d/%d added/changed/removed files\n' %
-      (branch,type,revision+1,max,len(added),len(changed),len(removed)))
+      (branch.decode('utf8'),type,revision+1,max,len(added),len(changed),len(removed)))
 
   for filename in removed:
     if fn_encoding:
       filename=filename.decode(fn_encoding).encode('utf8')
     filename=strip_leading_slash(filename)
-    if filename=='.hgsub':
+    if filename==b'.hgsub':
       remove_gitmodules(ctx)
-    wr('D %s' % filename)
+    wr(b'D %s' % filename)
 
   export_file_contents(ctx,man,added,hgtags,fn_encoding,plugins)
   export_file_contents(ctx,man,changed,hgtags,fn_encoding,plugins)
@@ -358,52 +379,54 @@ def export_note(ui,repo,revision,count,authors,encoding,is_first):
 
   parents = [p for p in repo.changelog.parentrevs(revision) if p >= 0]
 
-  wr('commit refs/notes/hg')
-  wr('committer %s %d %s' % (user,time,timezone))
-  wr('data 0')
+  wr(b'commit refs/notes/hg')
+  wr(b'committer %s %d %s' % (user,time,timezone))
+  wr(b'data 0')
   if is_first:
-    wr('from refs/notes/hg^0')
-  wr('N inline :%d' % (revision+1))
-  hg_hash=revsymbol(repo,str(revision)).hex()
-  wr('data %d' % (len(hg_hash)))
+    wr(b'from refs/notes/hg^0')
+  wr(b'N inline :%d' % (revision+1))
+  hg_hash=revsymbol(repo,b"%d" % revision).hex()
+  wr(b'data %d' % (len(hg_hash)))
   wr_no_nl(hg_hash)
   wr()
   return checkpoint(count)
 
-  wr('data %d' % (len(desc)+1)) # wtf?
-  wr(desc)
-  wr()
-
 def export_tags(ui,repo,old_marks,mapping_cache,count,authors,tagsmap):
   l=repo.tagslist()
   for tag,node in l:
     # Remap the branch name
     tag=sanitize_name(tag,"tag",tagsmap)
     # ignore latest revision
-    if tag=='tip': continue
+    if tag==b'tip': continue
     # ignore tags to nodes that are missing (ie, 'in the future')
-    if node.encode('hex_codec') not in mapping_cache:
-      sys.stderr.write('Tag %s refers to unseen node %s\n' % (tag, node.encode('hex_codec')))
+    if hexlify(node) not in mapping_cache:
+      sys.stderr.write(
+          'Tag %s refers to unseen node %s\n'
+          % (tag.decode('utf8'), hexlify(node).decode('utf8'))
+      )
       continue
 
-    rev=int(mapping_cache[node.encode('hex_codec')])
+    rev=int(mapping_cache[hexlify(node)])
 
     ref=revnum_to_revref(rev, old_marks)
     if ref==None:
       sys.stderr.write('Failed to find reference for creating tag'
           ' %s at r%d\n' % (tag,rev))
       continue
-    sys.stderr.write('Exporting tag [%s] at [hg r%d] [git %s]\n' % (tag,rev,ref))
-    wr('reset refs/tags/%s' % tag)
-    wr('from %s' % ref)
+    sys.stderr.write(
+        'Exporting tag [%s] at [hg r%d] [git %s]\n'
+        % (tag.decode('utf8'), rev, ref.decode('utf8'))
+    )
+    wr(b'reset refs/tags/%s' % tag)
+    wr(b'from %s' % ref)
     wr()
     count=checkpoint(count)
   return count
 
 def load_mapping(name, filename, mapping_is_raw):
-  raw_regexp=re.compile('^([^=]+)[ ]*=[ ]*(.+)$')
-  string_regexp='"(((\\.)|(\\")|[^"])*)"'
-  quoted_regexp=re.compile('^'+string_regexp+'[ ]*=[ ]*'+string_regexp+'$')
+  raw_regexp=re.compile(b'^([^=]+)[ ]*=[ ]*(.+)$')
+  string_regexp=b'"(((\\.)|(\\")|[^"])*)"'
+  quoted_regexp=re.compile(b'^'+string_regexp+b'[ ]*=[ ]*'+string_regexp+b'$')
 
   def parse_raw_line(line):
     m=raw_regexp.match(line)
@@ -415,22 +438,22 @@ def load_mapping(name, filename, mapping_is_raw):
     m=quoted_regexp.match(line)
     if m==None:
       return None
-    return (m.group(1).decode('string_escape'),
-            m.group(5).decode('string_escape'))
+    return (m.group(1).decode('unicode_escape').encode('utf8'),
+            m.group(5).decode('unicode_escape').encode('utf8'))
 
   cache={}
   if not os.path.exists(filename):
     sys.stderr.write('Could not open mapping file [%s]\n' % (filename))
     return cache
-  f=open(filename,'r')
+  f=open(filename,'rb')
   l=0
   a=0
   for line in f.readlines():
     l+=1
     line=line.strip()
-    if l==1 and line[0]=='#' and line=='# quoted-escaped-strings':
+    if l==1 and line[0:1]==b'#' and line==b'# quoted-escaped-strings':
       continue
-    elif line=='' or line[0]=='#':
+    elif line==b'' or line[0:1]==b'#':
       continue
     m=parse_raw_line(line) if mapping_is_raw else parse_quoted_line(line)
     if m==None:
@@ -454,7 +477,7 @@ def branchtip(repo, heads):
 
 def verify_heads(ui,repo,cache,force,branchesmap):
   branches={}
-  for bn, heads in repo.branchmap().iteritems():
+  for bn, heads in repo.branchmap().items():
     branches[bn] = branchtip(repo, heads)
   l=[(-repo.changelog.rev(n), n, t) for t, n in branches.items()]
   l.sort()
@@ -466,13 +489,16 @@ def verify_heads(ui,repo,cache,force,branchesmap):
     sha1=get_git_sha1(sanitized_name)
     c=cache.get(sanitized_name)
     if sha1!=c:
-      sys.stderr.write('Error: Branch [%s] modified outside hg-fast-export:'
-        '\n%s (repo) != %s (cache)\n' % (b,sha1,c))
+      sys.stderr.write(
+          'Error: Branch [%s] modified outside hg-fast-export:'
+          '\n%s (repo) != %s (cache)\n'
+          % (b.decode('utf8'), sha1.decode('utf8'), c.decode('utf8'))
+      )
       if not force: return False
 
   # verify that branch has exactly one head
   t={}
-  for h in repo.filtered('visible').heads():
+  for h in repo.filtered(b'visible').heads():
     (_,_,_,_,_,_,branch,_)=get_changeset(ui,repo,h)
     if t.get(branch,False):
       sys.stderr.write('Error: repository has at least one unnamed head: hg r%s\n' %
@@ -519,15 +545,15 @@ def hg2git(repourl,m,marksfile,mappingfile,headsfile,tipfile,
     max=tip
 
   for rev in range(0,max):
-  	(revnode,_,_,_,_,_,_,_)=get_changeset(ui,repo,rev,authors)
-  	if repo[revnode].hidden():
-  		continue
-  	mapping_cache[revnode.encode('hex_codec')] = str(rev)
+    (revnode,_,_,_,_,_,_,_)=get_changeset(ui,repo,rev,authors)
+    if repo[revnode].hidden():
+      continue
+    mapping_cache[hexlify(revnode)] = b"%d" % rev
 
   if submodule_mappings:
     # Make sure that all submodules are registered in the submodule-mappings file
     for rev in range(0,max):
-      ctx=revsymbol(repo,str(rev))
+      ctx=revsymbol(repo,b"%d" % rev)
       if ctx.hidden():
         continue
       if ctx.substate:
diff --git a/hg-fast-export.sh b/hg-fast-export.sh
index e1f2f50..06d791c 100755
--- a/hg-fast-export.sh
+++ b/hg-fast-export.sh
@@ -28,25 +28,20 @@ SFX_STATE="state"
 GFI_OPTS=""
 
 if [ -z "${PYTHON}" ]; then
-    # $PYTHON is not set, so we try to find a working python 2.7 to
-    # use. PEP 394 tells us to use 'python2', otherwise try plain
-    # 'python'.
-    if command -v python2 > /dev/null; then
-	PYTHON="python2"
-    elif command -v python > /dev/null; then
-	PYTHON="python"
-    else
-        echo "Could not find any python interpreter, please use the 'PYTHON'" \
-	     "environment variable to specify the interpreter to use."
-        exit 1
-    fi
+    # $PYTHON is not set, so we try to find a working python with mercurial:
+    for python_cmd in python2 python python3; do
+        if command -v $python_cmd > /dev/null; then
+            $python_cmd -c 'import mercurial' 2> /dev/null
+            if [ $? -eq 0 ]; then
+                PYTHON=$python_cmd
+                break
+            fi
+        fi
+    done
 fi
-
-# Check that the python specified by the user or autodetected above is
-# >= 2.7 and < 3.
-if ! ${PYTHON} -c 'import sys; v=sys.version_info; exit(0 if v.major == 2 and v.minor >= 7 else 1)' > /dev/null 2>&1 ; then
-    echo "${PYTHON} is not a working python 2.7 interpreter, please use the" \
-	 "'PYTHON' environment variable to specify the interpreter to use."
+if [ -z "${PYTHON}" ]; then
+    echo "Could not find a python interpreter with the mercurial module available. " \
+        "Please use the 'PYTHON' environment variable to specify the interpreter to use."
     exit 1
 fi
 
diff --git a/hg-reset.py b/hg-reset.py
index 2a36b1d..d91738b 100755
--- a/hg-reset.py
+++ b/hg-reset.py
@@ -7,6 +7,7 @@ from mercurial import node
 from hg2git import setup_repo,load_cache,get_changeset,get_git_sha1
 from optparse import OptionParser
 import sys
+from binascii import hexlify
 
 def heads(ui,repo,start=None,stop=None,max=None):
   # this is copied from mercurial/revlog.py and differs only in
@@ -24,7 +25,7 @@ def heads(ui,repo,start=None,stop=None,max=None):
   heads = {startrev: 1}
 
   parentrevs = repo.changelog.parentrevs
-  for r in xrange(startrev + 1, max):
+  for r in range(startrev + 1, max):
     for p in parentrevs(r):
       if p in reachable:
         if r not in stoprevs:
@@ -33,7 +34,7 @@ def heads(ui,repo,start=None,stop=None,max=None):
       if p in heads and p not in stoprevs:
         del heads[p]
 
-  return [(repo.changelog.node(r),str(r)) for r in heads]
+  return [(repo.changelog.node(r), b"%d" % r) for r in heads]
 
 def get_branches(ui,repo,heads_cache,marks_cache,mapping_cache,max):
   h=heads(ui,repo,max=max)
@@ -44,11 +45,11 @@ def get_branches(ui,repo,heads_cache,marks_cache,mapping_cache,max):
     _,_,user,(_,_),_,desc,branch,_=get_changeset(ui,repo,rev)
     del stale[branch]
     git_sha1=get_git_sha1(branch)
-    cache_sha1=marks_cache.get(str(int(rev)+1))
+    cache_sha1=marks_cache.get(b"%d" % (int(rev)+1))
     if git_sha1!=None and git_sha1==cache_sha1:
-      unchanged.append([branch,cache_sha1,rev,desc.split('\n')[0],user])
+      unchanged.append([branch,cache_sha1,rev,desc.split(b'\n')[0],user])
     else:
-      changed.append([branch,cache_sha1,rev,desc.split('\n')[0],user])
+      changed.append([branch,cache_sha1,rev,desc.split(b'\n')[0],user])
   changed.sort()
   unchanged.sort()
   return stale,changed,unchanged
@@ -57,20 +58,20 @@ def get_tags(ui,repo,marks_cache,mapping_cache,max):
   l=repo.tagslist()
   good,bad=[],[]
   for tag,node in l:
-    if tag=='tip': continue
-    rev=int(mapping_cache[node.encode('hex_codec')])
-    cache_sha1=marks_cache.get(str(int(rev)+1))
+    if tag==b'tip': continue
+    rev=int(mapping_cache[hexlify(node)])
+    cache_sha1=marks_cache.get(b"%d" % (int(rev)+1))
     _,_,user,(_,_),_,desc,branch,_=get_changeset(ui,repo,rev)
     if int(rev)>int(max):
-      bad.append([tag,branch,cache_sha1,rev,desc.split('\n')[0],user])
+      bad.append([tag,branch,cache_sha1,rev,desc.split(b'\n')[0],user])
     else:
-      good.append([tag,branch,cache_sha1,rev,desc.split('\n')[0],user])
+      good.append([tag,branch,cache_sha1,rev,desc.split(b'\n')[0],user])
   good.sort()
   bad.sort()
   return good,bad
 
 def mangle_mark(mark):
-  return str(int(mark)-1)
+  return b"%d" % (int(mark)-1)
 
 if __name__=='__main__':
   def bail(parser,opt):
@@ -107,7 +108,7 @@ if __name__=='__main__':
   state_cache=load_cache(options.statusfile)
   mapping_cache = load_cache(options.mappingfile)
 
-  l=int(state_cache.get('tip',options.revision))
+  l=int(state_cache.get(b'tip',options.revision))
   if options.revision+1>l:
     sys.stderr.write('Revision is beyond last revision imported: %d>%d\n' % (options.revision,l))
     sys.exit(1)
@@ -117,19 +118,39 @@ if __name__=='__main__':
   stale,changed,unchanged=get_branches(ui,repo,heads_cache,marks_cache,mapping_cache,options.revision+1)
   good,bad=get_tags(ui,repo,marks_cache,mapping_cache,options.revision+1)
 
-  print "Possibly stale branches:"
-  map(lambda b: sys.stdout.write('\t%s\n' % b),stale.keys())
+  print("Possibly stale branches:")
+  for b in stale:
+    sys.stdout.write('\t%s\n' % b.decode('utf8'))
 
-  print "Possibly stale tags:"
-  map(lambda b: sys.stdout.write('\t%s on %s (r%s)\n' % (b[0],b[1],b[3])),bad)
+  print("Possibly stale tags:")
+  for b in bad:
+    sys.stdout.write(
+      '\t%s on %s (r%s)\n'
+      % (b[0].decode('utf8'), b[1].decode('utf8'), b[3].decode('utf8'))
+    )
 
-  print "Unchanged branches:"
-  map(lambda b: sys.stdout.write('\t%s (r%s)\n' % (b[0],b[2])),unchanged)
+  print("Unchanged branches:")
+  for b in unchanged:
+    sys.stdout.write('\t%s (r%s)\n' % (b[0].decode('utf8'),b[2].decode('utf8')))
 
-  print "Unchanged tags:"
-  map(lambda b: sys.stdout.write('\t%s on %s (r%s)\n' % (b[0],b[1],b[3])),good)
+  print("Unchanged tags:")
+  for b in good:
+    sys.stdout.write(
+      '\t%s on %s (r%s)\n'
+      % (b[0].decode('utf8'), b[1].decode('utf8'), b[3].decode('utf8'))
+    )
 
-  print "Reset branches in '%s' to:" % options.headsfile
-  map(lambda b: sys.stdout.write('\t:%s %s\n\t\t(r%s: %s: %s)\n' % (b[0],b[1],b[2],b[4],b[3])),changed)
+  print("Reset branches in '%s' to:" % options.headsfile)
+  for b in changed:
+    sys.stdout.write(
+      '\t:%s %s\n\t\t(r%s: %s: %s)\n'
+      % (
+        b[0].decode('utf8'),
+        b[1].decode('utf8'),
+        b[2].decode('utf8'),
+        b[4].decode('utf8'),
+        b[3].decode('utf8'),
+      )
+    )
 
-  print "Reset ':tip' in '%s' to '%d'" % (options.statusfile,options.revision)
+  print("Reset ':tip' in '%s' to '%d'" % (options.statusfile,options.revision))
diff --git a/hg-reset.sh b/hg-reset.sh
index 453dbab..7370e34 100755
--- a/hg-reset.sh
+++ b/hg-reset.sh
@@ -11,7 +11,24 @@ SFX_MAPPING="mapping"
 SFX_HEADS="heads"
 SFX_STATE="state"
 QUIET=""
-PYTHON=${PYTHON:-python}
+
+if [ -z "${PYTHON}" ]; then
+    # $PYTHON is not set, so we try to find a working python with mercurial:
+    for python_cmd in python2 python python3; do
+        if command -v $python_cmd > /dev/null; then
+            $python_cmd -c 'import mercurial' 2> /dev/null
+            if [ $? -eq 0 ]; then
+                PYTHON=$python_cmd
+                break
+            fi
+        fi
+    done
+fi
+if [ -z "${PYTHON}" ]; then
+    echo "Could not find a python interpreter with the mercurial module available. " \
+        "Please use the 'PYTHON'environment variable to specify the interpreter to use."
+    exit 1
+fi
 
 USAGE="[-r <repo>] -R <rev>"
 LONG_USAGE="Print SHA1s of latest changes per branch up to <rev> useful
diff --git a/hg2git.py b/hg2git.py
index 1e740f1..991ca44 100755
--- a/hg2git.py
+++ b/hg2git.py
@@ -12,14 +12,21 @@ import os
 import sys
 import subprocess
 
+PY2 = sys.version_info.major < 3
+if PY2:
+  str = unicode
+  fsencode = lambda s: s.encode(sys.getfilesystemencoding())
+else:
+  from os import fsencode
+
 # default git branch name
-cfg_master='master'
+cfg_master=b'master'
 # default origin name
-origin_name=''
+origin_name=b''
 # silly regex to see if user field has email address
-user_re=re.compile('([^<]+) (<[^>]*>)$')
+user_re=re.compile(b'([^<]+) (<[^>]*>)$')
 # silly regex to clean out user names
-user_clean_re=re.compile('^["]([^"]+)["]$')
+user_clean_re=re.compile(b'^["]([^"]+)["]$')
 
 def set_default_branch(name):
   global cfg_master
@@ -34,26 +41,26 @@ def setup_repo(url):
     myui=ui.ui(interactive=False)
   except TypeError:
     myui=ui.ui()
-    myui.setconfig('ui', 'interactive', 'off')
+    myui.setconfig(b'ui', b'interactive', b'off')
     # Avoids a warning when the repository has obsolete markers
-    myui.setconfig('experimental', 'evolution.createmarkers', True)
-  return myui,hg.repository(myui,url).unfiltered()
+    myui.setconfig(b'experimental', b'evolution.createmarkers', True)
+  return myui,hg.repository(myui, fsencode(url)).unfiltered()
 
 def fixup_user(user,authors):
-  user=user.strip("\"")
+  user=user.strip(b"\"")
   if authors!=None:
     # if we have an authors table, try to get mapping
     # by defaulting to the current value of 'user'
     user=authors.get(user,user)
-  name,mail,m='','',user_re.match(user)
+  name,mail,m=b'',b'',user_re.match(user)
   if m==None:
     # if we don't have 'Name <mail>' syntax, extract name
     # and mail from hg helpers. this seems to work pretty well.
     # if email doesn't contain @, replace it with devnull@localhost
     name=templatefilters.person(user)
-    mail='<%s>' % templatefilters.email(user)
-    if '@' not in mail:
-      mail = '<devnull@localhost>'
+    mail=b'<%s>' % templatefilters.email(user)
+    if b'@' not in mail:
+      mail = b'<devnull@localhost>'
   else:
     # if we have 'Name <mail>' syntax, everything is fine :)
     name,mail=m.group(1),m.group(2)
@@ -62,15 +69,15 @@ def fixup_user(user,authors):
   m2=user_clean_re.match(name)
   if m2!=None:
     name=m2.group(1)
-  return '%s %s' % (name,mail)
+  return b'%s %s' % (name,mail)
 
 def get_branch(name):
   # 'HEAD' is the result of a bug in mutt's cvs->hg conversion,
   # other CVS imports may need it, too
-  if name=='HEAD' or name=='default' or name=='':
+  if name==b'HEAD' or name==b'default' or name==b'':
     name=cfg_master
   if origin_name:
-    return origin_name + '/' + name
+    return origin_name + b'/' + name
   return name
 
 def get_changeset(ui,repo,revision,authors={},encoding=''):
@@ -79,16 +86,16 @@ def get_changeset(ui,repo,revision,authors={},encoding=''):
   # how it fails
   try:
     node=repo.lookup(revision)
-  except hgerror.ProgrammingError:
-    node=binnode(revsymbol(repo,str(revision))) # We were given a numeric rev
+  except (TypeError, hgerror.ProgrammingError):
+    node=binnode(revsymbol(repo, b"%d" % revision)) # We were given a numeric rev
   except hgerror.RepoLookupError:
     node=revision # We got a raw hash
   (manifest,user,(time,timezone),files,desc,extra)=repo.changelog.read(node)
   if encoding:
     user=user.decode(encoding).encode('utf8')
     desc=desc.decode(encoding).encode('utf8')
-  tz="%+03d%02d" % (-timezone / 3600, ((-timezone % 3600) / 60))
-  branch=get_branch(extra.get('branch','master'))
+  tz=b"%+03d%02d" % (-timezone // 3600, ((-timezone % 3600) // 60))
+  branch=get_branch(extra.get(b'branch', b'master'))
   return (node,manifest,fixup_user(user,authors),(time,tz),files,desc,branch,extra)
 
 def mangle_key(key):
@@ -98,28 +105,33 @@ def load_cache(filename,get_key=mangle_key):
   cache={}
   if not os.path.exists(filename):
     return cache
-  f=open(filename,'r')
+  f=open(filename,'rb')
   l=0
   for line in f.readlines():
     l+=1
-    fields=line.split(' ')
-    if fields==None or not len(fields)==2 or fields[0][0]!=':':
+    fields=line.split(b' ')
+    if fields==None or not len(fields)==2 or fields[0][0:1]!=b':':
       sys.stderr.write('Invalid file format in [%s], line %d\n' % (filename,l))
       continue
     # put key:value in cache, key without ^:
-    cache[get_key(fields[0][1:])]=fields[1].split('\n')[0]
+    cache[get_key(fields[0][1:])]=fields[1].split(b'\n')[0]
   f.close()
   return cache
 
 def save_cache(filename,cache):
-  f=open(filename,'w+')
-  map(lambda x: f.write(':%s %s\n' % (str(x),str(cache.get(x)))),cache.keys())
+  f=open(filename,'wb')
+  for key, value in cache.items():
+    if not isinstance(key, bytes):
+      key = str(key).encode('utf8')
+    if not isinstance(value, bytes):
+      value = str(value).encode('utf8')
+    f.write(b':%s %s\n' % (key, value))
   f.close()
 
 def get_git_sha1(name,type='heads'):
   try:
     # use git-rev-parse to support packed refs
-    ref="refs/%s/%s" % (type,name)
+    ref="refs/%s/%s" % (type,name.decode('utf8'))
     l=subprocess.check_output(["git", "rev-parse", "--verify", "--quiet", ref])
     if l == None or len(l) == 0:
       return None
diff --git a/plugins/branch_name_in_commit/__init__.py b/plugins/branch_name_in_commit/__init__.py
index 910a446..311a84c 100644
--- a/plugins/branch_name_in_commit/__init__.py
+++ b/plugins/branch_name_in_commit/__init__.py
@@ -15,9 +15,11 @@ class Filter:
             raise ValueError("Unknown args: " + ','.join(args))
 
     def commit_message_filter(self, commit_data):
-        if not (self.skip_master and commit_data['branch'] == 'master'):
+        if not (self.skip_master and commit_data['branch'] == b'master'):
             if self.start:
-                sep = ': ' if self.sameline else '\n' 
+                sep = b': ' if self.sameline else b'\n'
                 commit_data['desc'] = commit_data['branch'] + sep + commit_data['desc']
             if self.end:
-                commit_data['desc'] = commit_data['desc'] + '\n' + commit_data['branch']
+                commit_data['desc'] = (
+                    commit_data['desc'] + b'\n' + commit_data['branch']
+                )
diff --git a/plugins/dos2unix/__init__.py b/plugins/dos2unix/__init__.py
index bf676a0..bae9358 100644
--- a/plugins/dos2unix/__init__.py
+++ b/plugins/dos2unix/__init__.py
@@ -8,4 +8,4 @@ class Filter():
     def file_data_filter(self,file_data):
         file_ctx = file_data['file_ctx']
         if not file_ctx.isbinary():
-            file_data['data'] = file_data['data'].replace('\r\n', '\n')
+            file_data['data'] = file_data['data'].replace(b'\r\n', b'\n')
diff --git a/plugins/issue_prefix/__init__.py b/plugins/issue_prefix/__init__.py
index b5a0fc6..5dd30b5 100644
--- a/plugins/issue_prefix/__init__.py
+++ b/plugins/issue_prefix/__init__.py
@@ -7,9 +7,11 @@ def build_filter(args):
 
 class Filter:
     def __init__(self, args):
+        if not isinstance(args, bytes):
+            args = args.encode('utf8') 
         self.prefix = args
 
     def commit_message_filter(self, commit_data):
-        for match in re.findall('#[1-9][0-9]+', commit_data['desc']):
+        for match in re.findall(b'#[1-9][0-9]+', commit_data['desc']):
             commit_data['desc'] = commit_data['desc'].replace(
-                match, '#%s%s' % (self.prefix, match[1:]))
+                match, b'#%s%s' % (self.prefix, match[1:]))
diff --git a/plugins/overwrite_null_messages/__init__.py b/plugins/overwrite_null_messages/__init__.py
index 3be7e53..b9ce512 100644
--- a/plugins/overwrite_null_messages/__init__.py
+++ b/plugins/overwrite_null_messages/__init__.py
@@ -4,13 +4,13 @@ def build_filter(args):
 class Filter:
     def __init__(self, args):
         if args == '':
-            message = '<empty commit message>'
+            message = b'<empty commit message>'
         else:
-            message = args
+            message = args.encode('utf8')
         self.message = message
 
     def commit_message_filter(self,commit_data):
         # Only write the commit message if the recorded commit
         # message is null.
-        if commit_data['desc'] == '\x00':
+        if commit_data['desc'] == b'\x00':
             commit_data['desc'] = self.message