Make flake8 a little stricter (#11326)

flake8 now correctly handles overloads

Author: hauntsaninja

setup.cfg

@@ -43,9 +43,8 @@ exclude =
 #   B007: Loop control variable not used within the loop body.
 #   B011: Don't use assert False
 #   F821: Name not defined (generates false positives with error codes)
-#   F811: Redefinition of unused function (causes annoying errors with overloads)
 #   E741: Ambiguous variable name
-extend-ignore = E128,W601,E701,E704,E402,B3,B006,B007,B011,F821,F811,E741
+extend-ignore = E128,W601,E701,E704,E402,B3,B006,B007,B011,F821,E741
 
 [coverage:run]
 branch = true

test-requirements.txt

@@ -1,7 +1,7 @@
 -r mypy-requirements.txt
 -r build-requirements.txt
 attrs>=18.0
-flake8>=3.8.1
+flake8==3.9.2
 flake8-bugbear
 flake8-pyi>=20.5
 lxml>=4.4.0