Add support for django 3.0

[yakky]

• [x] Replace ugettext_lazy with gettext_lazy when running on python 3
• [ ] Manual test paths not covered by test suite

[bunchesofdonald]

@yakky Anything I can do to help push this PR along? This is the last blocker for us to upgrade to Django 3.

[yakky]

@bunchesofdonald I just need to run it to cover code paths not included in tests Any additional review, tests will help!

[c0d5x]

Could this be merged?

[izimobil]

Merged, thank you very much @yakky