old_contents: version='0.1.2'
  release=False
  
  if not release:
      version += '.dev'
  
new_contents: version='0.1.2'
  release=False
  
  if not release:
      try:
          import subprocess
          proc = subprocess.Popen(['bzr', 'revno'], stdout=subprocess.PIPE)
          revno, errcode = proc.communicate()
          revno = int(revno)
          version += 'r%d' % revno
      except OSError:
          # bzr was probably not found
          # just tack on a dev label
          version += '.dev'
  
subject: Add bzr revno to version on non-release.