tests: optional PEP 657 error location in test-extension.t (
issue6781)
tests: filter out PEP 657 error locations in tracebacks (
issue6780)
https://docs.python.org/3/whatsnew/3.11.html#whatsnew311-pep657
pytype: add coverage for parts of hgext
There are tons of things to fix here (which have been blacklisted for now), but
this should help prevent further regressions.