flake8 failure for overload

[RonnyPfannschmidt]

followup to #5769

linting failed with

flake8...................................................................Failed
hookid: flake8

src/_pytest/python_api.py:16:1: TYP002 @overload is broken in <3.5.2, add `if sys.version_info < (3, 5, 2): def overload(f): return f`
src/_pytest/recwarn.py:10:1: TYP002 @overload is broken in <3.5.2, add `if sys.version_info < (3, 5, 2): def overload(f): return f`

i suspect a false positive due to the introduced compat import