PEP8 Compliance fixes.
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Merge pull request #513 from glogiotatidis/linting

Linting
Merge pull request #510 from akatsoulas/897881

[bug 897881] Remove Mozillians from an event's mail form.
[fix bug 911790] Display logo and site name in Persona login
Merge pull request #511 from hardfire/911790

[fix bug 911790] Display logo and site name in Persona login
[fix bug 927844] Use celery instead of cron in remozilla and voting apps.