interface cache can be simplified since we depend on zope.interface 5.0

[jamadden]

The try/except is not needed.

https://github.com/NextThought/nti.externalization/blob/907b3cda5b0121d42e2463503c57fe9a262f1ba9/src/nti/externalization/_interface_cache.py#L50-L57

Also, there's a subtle race-condition here if anyone tries to use _v_attrs later, as _make_modified_attributes does.

https://github.com/NextThought/nti.externalization/blob/907b3cda5b0121d42e2463503c57fe9a262f1ba9/src/nti/externalization/internalization/events.py#L55-L60

This low-level method should also return the _v_attrs dict (and maybe the providedBy object) it's using to avoid this.

[jamadden]

That race condition bites us because of zopefoundation/zope.container#38