Black's Changelog Entry and Lint checks that are run on PRs can contradict each other

[MarkCBell]

Describe the bug

The Changelog Entry Check which is run against PR's requires that CHANGES.md contains a reference the the PR.
However the Lint check runs prettier against CHANGES.md which can sometimes insist on breaking apart a PR reference.

To Reproduce

1. Add the following line to CHANGES.md:

  - `Black` now requires one-line docstrings to not have leading or trailing spaces (PR #1234)

2. Submit a PR containing this change.
3. The Lint / build (3.7) (pull_request) check will fail since this line is too long. It states that this needs to be changed to:

- `Black` now requires one-line docstrings to not have leading or trailing spaces (PR
  #1234)

However making this change results in the Changelog Entry Check (pull_request) failing since it's grep for "PR #1234" does not match the PR reference now that has been split over two lines.

Expected behavior

Changelog Entry Check should match for "PR #1234" even if it is split over multiple lines. So the formatting required by Black can be accepted.

Environment (please complete the following information):

• Version: master
• OS and Python version: Github action

Does this bug also happen on master?

Yes

[JelleZijlstra]

As a workaround, can you put the (PR part on the next line too?

We should ideally make the regex smarter so it accepts this though.

[MarkCBell]

As a workaround, can you put the (PR part on the next line too?

No. prettier will reject:

- `Black` now requires one-line docstrings to not have leading or trailing spaces
  (PR #1234)

and insist that this is also changed to:

- `Black` now requires one-line docstrings to not have leading or trailing spaces (PR
  #1234)