Log Message:
py-importlib-metadata: updated to 0.21

0.21
importlib.metadata now exposes the DistributionFinder metaclass and references \ 
it in the docs for extending the search algorithm.
Add Distribution.at for constructing a Distribution object from a known metadata \ 
directory on the file system.
Distribution finders now receive a context object that supplies .path and .name \ 
properties. This change introduces a fundamental backward incompatibility for \ 
any projects implementing a find_distributions method on a MetaPathFinder. This \ 
new layer of abstraction allows this context to be supplied directly or \ 
constructed on demand and opens the opportunity for a find_distributions method \ 
to solicit additional context from the caller.

0.20
Clarify in the docs that calls to .files could return None when the metadata is \ 
not present.
Return all requirements and not just the first for dist-info packages.