Fixing potential attribute access on None

Specifically when writing tests, the nav method in the settings
dashboard.py file can potentially attempt to access slug on None.

Closes-bug: #1291050

Change-Id: I6df58d26f5df71ac7c605c5d77b9aa9d8d811956
Fix selenium imports on tests

tests require selenium to be installed, no matter if
integration tests or selenium tests are executed or
not.

Change-Id: Ie55d64c19b00b5b22f62948d4a24a3f322082b0c
Closes-Bug: #1289270
No need to mark strings in test_plugin translatable

Change-Id: I3f993163b60302bbaa87c049c19631e1b978886b
Closes-Bug: #1291505
Merge "Fix selenium imports on tests"
Merge "Fixing potential attribute access on None"