[Bug] AssertionError in multithread context

[Jasha10]

I ran into an AssertionError using Hydra with python's threading library.

In theory, Hydra is not thread safe. However, we should be able to support using Hydra in a multithread application if Hydra is only used from one thread.

Here is the relevant part of the traceback:

An error occurred during Hydra's exception formatting:
AssertionError()
Traceback (most recent call last):
  File "/home/jasha10/miniconda3/envs/pysc/lib/python3.9/site-packages/hydra/_internal/utils.py", line 252, in run_and_report
    assert mdl is not None
AssertionError

[qmpzzpmq]

same issue

[Jasha10]

@qmpzzpmq I've opened PR #2011 to close this issue, would you mind testing it out?

[Jasha10]

Unfortunately I forgot how to reproduce this issue. I'll close this now and will reopen it if anyone can post a repro here in the future.