PR Summary

The test is already skipped if the boilerplate script is missing (i.e., not a git checkout), but should also be skipped if black is not installed.

Also, the boilerplate script ignored if running black failed, leading the test to show lots of line differences instead of just erroring out earlier.

PR Checklist

Documentation and Tests

• Has pytest style unit tests (and pytest passes)
• [n/a] Documentation is sphinx and numpydoc compliant (the docs should build without error).
• [n/a] New plotting related features are documented with examples.

Release Notes

• [n/a] New features are marked with a .. versionadded:: directive in the docstring and documented in doc/users/next_whats_new/
• [n/a] API changes are marked with a .. versionchanged:: directive in the docstring and documented in doc/api/next_api_changes/
• [n/a] Release notes conform with instructions in next_whats_new/README.rst or next_api_changes/README.rst