We occasionally see this error:

pants.core.util_rules.lockfile_metadata.InvalidLockfileError: You are using the lockfile at 3rdparty/python/lockfiles/mypy.txt to install the tool `mypy`, but it is not compatible with your configuration:

- You have set different requirements than those used to generate the lockfile. You can fix this by updating `[mypy].version`, `[mypy].source_plugins`, and/or `[mypy].extra_requirements`, or by using a new custom lockfile.
In the lockfile, but not in the input requirements: ['pytest==5.4.3']

To regenerate your lockfile based on your current configuration, run `./pants generate-lockfiles --resolve=mypy`.

Now begs the question why this

pytest

requirement seems to be coming and going, as if we regenerate the mypy lockfile, the issue goes away, but then it comes back sometimes after we regenerate the lockfile for pyhon-default.. I’ve not yet figured out the exact pattern, but if anyone recognizes this issue.. ?

(another question is if it should be a hard error when there’s an additional unused input in the lockfile rather than a missing one?)

OK, found it. It was a

[mypy].source_plugins

entry that points to code that pulled in

pytest

irrationally..