Switch to signed tag commits as more transparent upstream sources.

Replace python-pytest-runner with python-pytest in checkdepends.

Add missing dependency on python-typing-extensions:
https://bugs.archlinux.org/task/80234

Set SPDX license identifier according to upstream information

Switch to github release tarballs because pypi dropped support for PGP signed sources.

archlinux/devtools!109 (comment 74475)

Remove unneeded quotes and curly braces.
Switch to PEP517.

Remove unneeded prepare() by explicitly not using a pytest config.

Simplify quoting in file.
Simplify installation in package() to adhere to python package guidelines.

Remove patch to fix setup.py (problem fixed upstream).

Apply upstream provided patch to prevent tests from being installed top-level.

Dropping python2 support. Updating maintainer. Adding docs. Running tests directly via pytest. Minor cleanups.