Update black to 21.5b2

[pyup-bot]

This PR updates black from 21.4b1 to 21.5b2.

Changelog

21.5b2

_Black_

- A space is no longer inserted into empty docstrings (2249)
- Fix handling of .gitignore files containing non-ASCII characters on Windows (2229)
- Respect `.gitignore` files in all levels, not only `root/.gitignore` file (apply
`.gitignore` rules like `git` does) (2225)
- Restored compatibility with Click 8.0 on Python 3.6 when LANG=C used (2227)
- Add extra uvloop install + import support if in python env (2258)
- Fix --experimental-string-processing crash when matching parens are not found (2283)
- Make sure to split lines that start with a string operator (2286)
- Fix regular expression that black uses to identify f-expressions (2287)

_Blackd_

- Add a lower bound for the `aiohttp-cors` dependency. Only 0.4.0 or higher is
supported. (2231)

_Packaging_

- Release self-contained x86_64 MacOS binaries as part of the GitHub release pipeline
(2198)
- Always build binaries with the latest available Python (2260)

Documentation

- Add discussion of magic comments to FAQ page (2272)
- `--experimental-string-processing` will be enabled by default in the future (2273)
- Fix typos discovered by codespell (2228)
- Fix Vim plugin installation instructions. (2235)
- Add new Frequently Asked Questions page (2247)
- Fix encoding + symlink issues preventing proper build on Windows (2262)

21.5b1

_Black_

- Refactor `src/black/__init__.py` into many files (2206)

Documentation

- Replaced all remaining references to the
[`master`](https://github.com/psf/black/tree/main) branch with the
[`main`](https://github.com/psf/black/tree/main) branch. Some additional changes in
the source code were also made. (2210)
- Sigificantly reorganized the documentation to make much more sense. Check them out by
heading over to [the stable docs on RTD](https://black.readthedocs.io/en/stable/).
(2174)

21.5b0

_Black_

- Set `--pyi` mode if `--stdin-filename` ends in `.pyi` (2169)
- Stop detecting target version as Python 3.9+ with pre-PEP-614 decorators that are
being called but with no arguments (2182)

_Black-Primer_

- Add `--no-diff` to black-primer to suppress formatting changes (2187)

21.4b2

_Black_

- Fix crash if the user configuration directory is inaccessible. (2158)

- Clarify
[circumstances](https://github.com/psf/black/blob/master/docs/the_black_code_style.md#pragmatism)
in which _Black_ may change the AST (2159)

- Allow `.gitignore` rules to be overridden by specifying `exclude` in `pyproject.toml`
or on the command line. (2170)

_Packaging_

- Install `primer.json` (used by `black-primer` by default) with black. (2154)

Links

• PyPI: https://pypi.org/project/black
• Changelog: https://pyup.io/changelogs/black/
• Repo: https://github.com/psf/black

[pyup-bot]

Closing this in favor of #227