fix: remove libcst as a required dependency

[adamchainz]

libcst is only used for a one-off "fixup" script. It’s not necessary to always depend on it.

It caused an issue on one project as old libcst versions don't ship macOS M1 wheels, and it took time to figure this out.

(Also the instructions for using the fixup script were incorrect.)

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• [nope] Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• [I hope so] Ensure the tests and linter pass
• [it shouldn't] Code coverage does not decrease (if any source code was changed)
• [yes] Appropriate docs were updated (if necessary)

Fixes #395 🦕

[tswast]

Thanks for the fix! I agree that this dependency is not necessary in most cases.

[adamchainz]

Would you be able to replicate this to other google python packages? In just the one google project I work on I see many other google packages depend on libcst for similar scripts: google-cloud-kms, google-cloud-pubsub, google-cloud-secret-manager, etc.

[tswast]

Would you be able to replicate this to other google python packages? In just the one google project I work on I see many other google packages depend on libcst for similar scripts: google-cloud-kms, google-cloud-pubsub, google-cloud-secret-manager, etc.

I only maintain the BigQuery-related packages, but I'll bring this up with our core Python team.

[buhrmann]

Btw, although this has been fixed almost a year ago, there is no version of this (>=2.12) on conda-forge still. Not sure whether you officially support conda packages, but at the moment only pypi seems to work.