old_contents: 
  # FIXME: duplicated
  which_packages = [
      (u'worldbank-tz', True),
      (u'unops-tz', True),
      (u'dfid-tz', True),
      (u'unitedstates-tz', True),
      (u'dfid-org', True),
      (u'dfid-ug', True)
      ]
  
new_contents: 
  # FIXME: duplicated
  which_packages = [
      (u'dfid-ml', True),
      (u'dfid-589', True),
      (u'dfid-ph', True),
      (u'worldbank-789', True),
      (u'worldbank-ao', True),
      ]
  
subject: Update which_packages