500 error when making a submission and addJob call fails

[20wildmanj]

When making a submission to an autograded assignment, if tango_add_job receives a failed response from Tango (such as if docker is not running), then it will cause the user to receive a 500 error, instead of being properly handled. The error should be caught by handin and properly redirect the user / display the error if they are priveleged.

[damianhxy]

So I was initially able to reproduce this, but after investigating for a while it seemed to fix itself ...?