===================
- Require Python 3.9 or later (breaking change).
- Remove ``MRUCache`` and the ``func.mru_cache`` decorator (breaking
change).
- Add an optional ``condition`` parameter to the ``cached`` and
``cachedmethod`` decorators, which, when used with a
``threading.Condition`` instance, should improve `cache stampede
<https://en.wikipedia.org/wiki/Cache_stampede>`_ issues in massively
parallel environments. Note that this will incur some performance
penalty, and therefore has to be enabled explicitly.
- Convert the ``cachetools.func`` decorators to use a
``threading.Condition`` instance to deal with `cache stampede
<https://en.wikipedia.org/wiki/Cache_stampede>`_ issues. Note that
this *may* result in a noticable performance degradation, depending
on your actual use case.
- Update CI environment.