py3: use email.parser module to parse email messages

Before this patch we use email.Parser.Parser() from the email module which is
not available on Python 3.

On Python 2:

>>> import email
>>> import email.parser as emailparser
>>> email.Parser.Parser is emailparser.Parser
True

hgext/convert/gnuarch.py

@@ -7,7 +7,7 b''
 # GNU General Public License version 2 or any later version.
 from __future__ import absolute_import
 
-import email
+import email.parser as emailparser
 import os
 import shutil
 import stat
@@ -63,7 +63,7 b' class gnuarch_source(common.converter_so'
         self.changes = {}
         self.parents = {}
         self.tags = {}
-        self.catlogparser = email.Parser.Parser()
+        self.catlogparser = emailparser.Parser()
         self.encoding = encoding.encoding
         self.archives = []
 

hgext/notify.py

@@ -135,6 +135,7 b' web.baseurl'
 from __future__ import absolute_import
 
 import email
+import email.parser as emailparser
 import fnmatch
 import socket
 import time
@@ -339,7 +340,7 b' class notifier(object):'
                           'and revset\n')
             return
 
-        p = email.Parser.Parser()
+        p = emailparser.Parser()
         try:
             msg = p.parsestr(data)
         except email.Errors.MessageParseError as inst:

mercurial/patch.py

@@ -12,6 +12,7 b' import collections'
 import copy
 import difflib
 import email
+import email.parser as emailparser
 import errno
 import hashlib
 import os
@@ -108,7 +109,7 b' def split(stream):'
             cur.append(line)
         c = chunk(cur)
 
-        m = email.Parser.Parser().parse(c)
+        m = emailparser.Parser().parse(c)
         if not m.is_multipart():
             yield msgfp(m)
         else:
@@ -217,7 +218,7 b' def extract(ui, fileobj):'
     fd, tmpname = tempfile.mkstemp(prefix='hg-patch-')
     tmpfp = os.fdopen(fd, pycompat.sysstr('w'))
     try:
-        msg = email.Parser.Parser().parse(fileobj)
+        msg = emailparser.Parser().parse(fileobj)
 
         subject = msg['Subject'] and mail.headdecode(msg['Subject'])
         data['user'] = msg['From'] and mail.headdecode(msg['From'])