extract_messages command failing without Genshi

[Jun Omae]

$ /dev/shm/trac-trunk/bin/python setup.py extract_messages
...
extracting messages from trac/templates/genshi/about.html (line_comment_prefix="##", line_statement_prefix="#", trim_blocks="yes", newstyle_gettext="yes", variable_start_string="${", extensions="jinja2.ext.with_", variable_end_string="}", lstrip_blocks="yes")
Traceback (most recent call last):
  File "setup.py", line 158, in <module>
    **extra
  File "/usr/lib/python2.7/distutils/core.py", line 151, in setup
    dist.run_commands()
  File "/usr/lib/python2.7/distutils/dist.py", line 953, in run_commands
    self.run_command(cmd)
  File "/usr/lib/python2.7/distutils/dist.py", line 972, in run_command
    cmd_obj.run()
  File "/dev/shm/trac-trunk/local/lib/python2.7/site-packages/babel/messages/frontend.py", line 467, in run
    for filename, lineno, message, comments, context in extracted:
  File "/dev/shm/trac-trunk/local/lib/python2.7/site-packages/babel/messages/extract.py", line 156, in extract_from_dir
    dirpath=absname,
  File "/dev/shm/trac-trunk/local/lib/python2.7/site-packages/babel/messages/extract.py", line 211, in check_and_call_extract_file
    strip_comment_tags=strip_comment_tags
  File "/dev/shm/trac-trunk/local/lib/python2.7/site-packages/babel/messages/extract.py", line 240, in extract_from_file
    strip_comment_tags))
  File "/dev/shm/trac-trunk/local/lib/python2.7/site-packages/babel/messages/extract.py", line 321, in extract
    for lineno, funcname, messages, comments in results:
  File "/home/jun66j5/src/tracdev/git/trac/dist.py", line 319, in extract_html
    for m in extractor(fileobj, keywords, comment_tags, options):
TypeError: 'NoneType' object is not callable
make: *** [extract] Error 1

Python: /dev/shm/trac-trunk/bin/python

  Package        Version
  ------------------------------------------------------
  Python       : 2.7.6 (default, Jun 22 2015, 17:58:13)
               : [GCC 4.8.2]
  Setuptools   : 36.0.1
  Jinja2       : 2.9.6
  Genshi       : not installed
  Babel        : 2.4.0
  sqlite3      : 2.6.0 (3.8.2)
  PySqlite     : not installed
  PyMySQL      : not installed
  Psycopg2     : not installed
  SVN bindings : not installed
  Mercurial    : not installed
  Pygments     : not installed
  Textile      : not installed
  Pytz         : 2017.2
  Docutils     : not installed
  Twill        : not installed
  LXML         : not installed
  coverage     : not installed
  figleaf      : not installed

Variables:
  PATH=/dev/shm/trac-trunk/bin:/home/jun66j5/bin:/home/jun66j5/venv/tools/bin:/home/jun66j5/.gem/ruby/2.0.0/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
  PYTHONPATH=.
  TRAC_TEST_DB_URI=
  server-options= -p 3000 -a '*,/home/jun66j5/src/trac-htdigest.txt,auth'  -e

External dependencies:
  Git version: git version 1.9.1
  Subversion version: 1.8.8

That command works with Genshi.