Keyring 22.4.0+ fails to be imported in Python 3.8+

[ccordoba12]

Describe the bug

Keyring fails to be imported in Python 3.8+ due to this import:

keyring/keyring/backend.py

Line 12 in bab15d0

import importlib_metadata as metadata

Since that functionality is part of the standard library in Python 3.8+, it needs to written as

import importlib.metadata as metadata

for those versions (I understand the import is correct for older ones).

To Reproduce
Steps to reproduce the behavior:

1. Install Keyring 22.4.0 or later in Python 3.8+
2. Open a Python interpreter
3. import keyring

Expected behavior
Keyring shouldn't fail when imported.

Environment

• OS: Any operating system. This was discovered in Conda-forge when creating packages for Keyring:

  keyring v22.4.0 conda-forge/keyring-feedstock#62

[Zac-HD]

Came here with a similar report; the trick is to make the dependency conditional on Python version and then to try importing the stdlib version before falling back to the backport on ImportError. https://github.com/HypothesisWorks/hypothesis/search?q=importlib_metadata shows how we do that in Hypothesis (which indirectly depends on keyring - so thanks 🥰)

[Zac-HD]

Based on the failing CI for #502, I think we're just asking for 473465e to be reverted... it's a nicer interface for the implementation of keyring, but as a consumer of the code I'd prefer to avoid the extra dependency 😕

[jaraco]

As reported, this issue is invalid. As can be clearly seen in 473465e, Keyring intentionally added the dependency for additional Python versions to adopt new features in importlib_metadata 3.6. The recommendation is to install the package with its declared dependencies and everything should work as designed.

Please let me know if I can advise conda on how to support this change.