Segmentation fault on pytest exit when creating a SerializableObjectWithMetadata

A user reported that there is a segmentation fault when running pytest + objects with metadata + the "fs" (fake filesystem) capture system.

Repro:
```python
import opentimelineio as otio

# Does not segfault if you comment out this "test"
def test_empty_fs(fs):
pass

def test_create_clip(capsys):
# can be child classes of SerializableObjectWithMetadata (Clip, Gap, etc),
# however other otio C++ classes appear to be ok (RationalTime, TimeRange,
# TimeTransform)
otio.core.SerializableObjectWithMetadata(
# also does not segfault if you comment this out
metadata={}
)
```

Output:
```
❯ pytest otio_pytest_seg_fault.py --disable-warnings
============================================== test session starts ===============================================
platform darwin -- Python 3.8.13, pytest-7.2.0, pluggy-1.0.0
rootdir: /private/var/tmp
plugins: pyfakefs-5.0.0
collected 2 items

otio_pytest_seg_fault.py .. [100%]

========================================== 2 passed, 1 warning in 0.09s ==========================================
zsh: segmentation fault pytest otio_pytest_seg_fault.py --disable-warnings
```

(The warning is related to our use of `imp` and appears to be a red herring)

Start by running the provided pytest reproduction with the pyfakefs `fs` fixture, `capsys`, and an empty metadata dictionary. Compare the exit behavior with metadata omitted and with the other listed OpenTimelineIO C++ classes. Done means the reproduction completes without a segmentation fault on pytest exit while preserving the affected object behavior.

Written by the indexing model from the issue text.