pyupgrade: drop usage of py3 aliases for `OSError` These were different classes in py2, but now a handful of error classes are just an alias of `OSError`, like `IOError`, `EnvironmentError`, `WindowsError`, etc. This is the result of running a hacked version of `pyupgrade` 3.19.1[1] $ hg files -0 'relglob:**.py' | xargs -0 \ pyupgrade --py38-plus --keep-percent-format --keep-mock --keep-runtime-typing The hack is because it doesn't have command line switches to disable most changes, so it makes tons of unrelated changes all at once. The hack is to 1) patch `pyupgrade._main._fix_tokens()` to immediately return its content arg 2) change `pyupgrade._data.register_decorator()` to only register the function if it's from the fixer we're interested in: if func.__module__ in ( "pyupgrade._plugins.exceptions", ): FUNCS[tp].append(func) return func [1] https://github.com/asottile/pyupgrade