add test to detect celery/pyramid-registry problematic resolution

[fmigneault]

To Do

• [x] patch get_registry and relevant methods such that test succeeds
• [ ] validate against running / live server where issue was observed (@perronld)
• [x] extend test for more cases if not resolved entirely
• [x] update changelog

References

• Closes #589 (once actually fixed)

[fmigneault]

@perronld Just need a counter validation to make sure I didn't reintroduce the problem.

[codecov[bot]]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (2752c63) 85.17% compared to head (bb8cdb4) 85.17%.

Files	Patch %	Lines
weaver/__init__.py	0.00%	2 Missing :warning:
weaver/utils.py	81.81%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #590 +/- ## ======================================= Coverage 85.17% 85.17% ======================================= Files 79 79 Lines 18023 18035 +12 Branches 2728 2731 +3 ======================================= + Hits 15351 15362 +11 - Misses 1941 1942 +1 Partials 731 731 ```

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