old_contents: from __future__ import absolute_import, unicode_literals
  from .premailer import Premailer, transform
  
  __version__ = '3.1.0'
  
new_contents: from __future__ import absolute_import, unicode_literals
  from .premailer import Premailer, transform
  
  __version__ = '3.1.1'
  
subject: bump to version 3.1.1