mypy: fix ci, use a newer flake8 and flake8-pyi, ignore a new error (python#8812)

Co-authored-by: hauntsaninja <>

Author: hauntsaninja

setup.cfg

@@ -43,7 +43,8 @@ exclude =
 #   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)
-extend-ignore = E128,W601,E701,E704,E402,B3,B006,B007,B011,F821,F811
+#   E741: Ambiguous variable name
+extend-ignore = E128,W601,E701,E704,E402,B3,B006,B007,B011,F821,F811,E741
 
 [coverage:run]
 branch = true

test-requirements.txt

@@ -1,8 +1,8 @@
 -r mypy-requirements.txt
 attrs>=18.0
-flake8>=3.7
+flake8>=3.8.1
 flake8-bugbear; python_version >= '3.5'
-flake8-pyi; python_version >= '3.6'
+flake8-pyi>=20.5; python_version >= '3.6'
 lxml>=4.4.0
 psutil>=4.0
 pytest==5.3.2