Integration test
Useful error message on 401
Implement review suggestions
Add unit test for 401
Split long line
Merge pull request #171 from SUSE/review_140908_error_on_stale_credentials_2156

[Review] Request from 'wstephenson' @ 'SUSE/connect/review_140908_error_on_stale_credentials_2156'
Having responded to Artem's comments, merging.