The with_wheel fixture doesn't have a value and isn't ever referenced
within a test function.

To avoid typing it every test function, change tests to use
pytest.mark.usefixture. It will no longer appear as an argument.

https://docs.pytest.org/en/latest/how-to/fixtures.html#use-fixtures-in-classes-and-modules-with-usefixtures

Install pytest in mypy environment

This issue template has been superseeded by the new YAML forms, so we can remove it.

This will help with issues that are being flagged as warnings by Sphinx.

Add a dedicated page for "Requirements File Format"

Remove unused class TestUpgradeDistributeToSetuptools

Simplify vendoring configuration

The msgpack-python was replaced by msgpack. This removes the need to
special case its directory.

The pytoml library is no longer vendored.

The resolvelib package distributes its license and so doesn't require a
license fallback URL.

Bump to vendoring 1.0.x

This now supports:

- Clearer failure mode, for imports of the format `import x.y`
- Regular expression support for dropping files (useful for when we vendor pygments)
- Patching files prior to rewriting imports, allowing generation of patches on the
  original package sources.
- Detection of py.typed files, which omits generation of unnecessary `.pyi` stubs.

pytest includes type annotations and is PEP-561 compliant. This helps
ensure correct pytest API usage.

This caught a misuse of pytest.mark.skipif which did not include a
boolean argument. The test is now marked "network" and no longer
skipped.

Handle TODO comment in tests/functional/test_new_resolver.py

Replace assert_raises_regexp function with pytest.raises

Unused since 6b541457 when the last test
method was removed.

Removing the class avoids the need to add type annotations.

Co-authored-by: NPaul Moore <p.f.moore@gmail.com>

setuptools removed use_2to3 in version v58.0.1 (2021-09-06). Some tests
install the anyjson package which uses this feature and so those tests
result in a command failure. The failure appeared as:

    error in anyjson setup command: use_2to3 is invalid.

As anyjson package is no longer maintained (last release was 2012),
change the tests to use a package that is healthy.

For details on the setuptools change, see the history at:

https://setuptools.readthedocs.io/en/latest/history.html#v58-0-2

This is basically based on a wild guess, that the search engines would
rank this higher in searches about requirements.txt files, if we mention
the file explicitly here.

This is a better, more visible location for this file format. It is more
discoverable and more likely to show up in search results.

This was originally the reference to the command line interface for pip.
That is now handled by cli/ pages, which frees up these pages for
describing other aspects of pip.

There was also one unused monkeypatch fixture removed.

Remove unnecessary html.unescape() calls in index/collector.py

Replace use of pretend library with unitest.mock in tests

Remove unused monkeypatch fixtures in tests

Harmonize type signature of Command.run()

Fix docs build failure

Resolves Sphinx error:

    .../pip/docs/html/user_guide.rst:1011:undefined label: dependency resolution backtracking