Add exception for two-factor required

[JonnyWong16]

Description

Add a separate exception for two-factor required on login.

Refer to tools/plex-gettoken.py for an example.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the docstring for new or existing methods
• I have added tests when applicable