Issue #95: Error 500 on approving pull request when "Approved" translation is unicode (conservancy/kallithea)

[Gummy35]

New issue 95: Error 500 on approving pull request when "Approved" translation is unicode
https://bitbucket.org/conservancy/kallithea/issue/95/error-500-on-approving-pull-request-when

Gummy35:

traced it to model/notification.py,

Fix :

replace

```
#!python

l = [str(x) for x in [kwargs.get('status_change'), kwargs.get('closing_pr') and _('Closing')] if x]

```

with 

```
#!python

l = [unicode(x) for x in [kwargs.get('status_change'), kwargs.get('closing_pr') and _('Closing')] if x]

```