Fix CI with latest flake8-bugbear (#3412)

Author: JelleZijlstra

.flake8

@@ -1,5 +1,6 @@
 [flake8]
-ignore = E203, E266, E501, W503
+# B905 should be enabled when we drop support for 3.9
+ignore = E203, E266, E501, W503, B905
 # line length is intentionally set to 80 here because black uses Bugbear
 # See https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#line-length for more details
 max-line-length = 80