oidc-auth does not respond well to misconfiguration of dex

[Michel Thebeau [WIND]]

Brief Description
-----------------
When dex is misconfigured, or when there is a network error, an authentication request using 'oidc-auth' generates a python trace from unhandled exception with message "HTTP Error 500: Internal Server Error", or similar

Severity
--------
Minor

Steps to Reproduce
------------------
Apply the oidc/dex application per starlingx documentation and verify the correct behaviour and login using oidc-auth command. Apply a mis-configuration, such as incorrect baseDN for UserSearch, and retry the oidc-auth. Incorrect configuration will yield 500 internal server error. While induced network failure yields response code 200 with timeout reason.

Expected Behavior
------------------
Especially, no traceback. Preferable to have appropriate responses for known conditions, suggested actions.

Actual Behavior
----------------
Python stack trace, for example:

    Traceback (most recent call last):
      File "/usr/bin/oidc-auth", line 10, in <module>
        sys.exit(main())
      File "/usr/lib/python3/dist-packages/oidcauthtools/oidc_auth.py", line 110, in main
        dexLoginGrantAccessResponse = br.submit()
      File "/usr/lib/python3/dist-packages/mechanize/_mechanize.py", line 697, in submit
        return self.open(self.click(*args, **kwds))
      File "/usr/lib/python3/dist-packages/mechanize/_mechanize.py", line 257, in open
        return self._mech_open(url_or_request, data, timeout=timeout)
      File "/usr/lib/python3/dist-packages/mechanize/_mechanize.py", line 313, in _mech_open
        raise response
    mechanize._response.httperror_seek_wrapper: HTTP Error 500: Internal Server Error

Reproducibility
---------------
100%

System Configuration
--------------------
Any configuration, with oidc-auth-apps application

Branch/Pull Time/Commit
-----------------------
starlingx master

Last Pass
---------
n/a

Timestamp/Logs
--------------
N/A, trace for oidc-auth command as noted above. In the example of incorrect configuration the dex pod log clarifies the misconfiguration as ldap referral response:

time="2022-10-04T17:33:42Z" level=info msg="performing ldap search <snip>baseDN, etc</snip>"
time="2022-10-04T17:33:42Z" level=error msg="Failed to login user: ldap: search with filter "<snip>user info</snip>" failed: LDAP Result Code 10 \"Referral\": <snip>private stuff</snip>

Test Activity
-------------
manual regression

Workaround
----------
n/a

[Michel Thebeau [WIND] (mthebeau)]

Merged to starlingx master:
https://review.opendev.org/c/starlingx/oidc-auth-armada-app/+/886996
https://opendev.org/starlingx/oidc-auth-armada-app/commit/cc9186a7f979664004a0b1671be06528f93486dd

Zuul is being silent about it, but I'm not sure why.

[Ghada Khalil (gkhalil)]

The required reviews merged. Marking as Fix Released
https://review.opendev.org/c/starlingx/oidc-auth-armada-app/+/886997
https://review.opendev.org/c/starlingx/oidc-auth-armada-app/+/886996