[Merge] lp:~sjakthol/update-manager/fix-slow-calculation into lp:update-manager

[Sami Jaktholm]

Fixed those errors. Apparently no warning or error message is shown if you don't have pep8 or pyflakes installed...
-- 
https://code.launchpad.net/~sjakthol/update-manager/fix-slow-calculation/+merge/161284
Your team Ubuntu Core Development Team is requested to review the proposed merge of lp:~sjakthol/update-manager/fix-slow-calculation into lp:update-manager.