templates/changelog-rss.tmpl

support hooks written in python.

to write hook in python, create module with hook function inside.
make sure mercurial can import module (put it in $PYTHONPATH or load it
as extension).  hook function should look like this:

def myhook(ui, repo, hooktype, **kwargs):
   if hook_passes:
      return True
   elif hook_explicitly_fails:
      return False
   elif some_other_failure:
      import util
      raise util.Abort('helpful failure message')
   else:
      return
      # implicit return of None makes hook fail!

then in .hgrc, add hook with "python:" prefix:

[hooks]
commit = python:mymodule.myhook

#header#
    <title>#repo|escape# Changelog</title>
    <description>#repo|escape# Changelog</description>
    #entries%changelogentry#
  </channel>
</rss>