add failing test
apply the fix
add template NEWS entry according to https://pip.pypa.io/en/latest/development/contributing/#news-entries (wrong PR #)
rename news entry to the current PR #
respond to review comments
fix test failures
fix tests by adding uuid salt in urls
cache html page fetching by link
make CI pass (?)
make the types much better
finally listen to the maintainer and cache parse_links() by url :)
avoid caching parse_links() when the url is an index url
cleanup
add testing for uncachable marking
only conditionally vendor _lru_cache for py2
bugfix => feature
python 2 does not cache!
Do away with type: ignore with getattr()
respond to review comments
This is the standard type used by packaging.tags. Making this change
throughout the code lets us start switching over to using its
tag-generating functions in get_supported().
We also get rid of a test, since it was superseded by `__str__` in
packaging.tags.Tag.
Why: To better group code that handles index interactions.
Renames pip._internal.{collector -> index.collector} and
pip._internal.{index -> index.package_finder}
