Provide celery logs on task failure / general error transparency

[laurashub]

Tasks like training models and saving grades don't provide any feedback about why they fail, it may be useful to the user to dump logs to a file on task failure.

[laurashub]

Working on making the logs persistent, but in the meantime I also added error transparency on the frontend as well by allowing the caught python exceptions in celery tasks to pass through - ex:

Other potential instances when errors can happen that we want to communicate are interaction calculation, saving to the database, and predicting on not-yet-seen molecules, so I'll be updating those to pass through on failure as well.