Problem: Appending the login backends was not reliable enough to make tests pass
Problem: Appending the login backends was not reliable enough to make tests pass

Solution: Changed `modify_settings` and append to: `override_settings`. This means if you have the mock login in your local.py the tests which expect failures and certain usernames would still pass.

CCI-MOC/GUI-Backend,CCI-MOC/GUI-Backend,CCI-MOC/GUI-Backend,CCI-MOC/GUI-Backend