Add flake8 ignore for black compatibility

pyproject.toml

@@ -77,6 +77,7 @@ extend-ignore = [
     "E203", # See https://github.com/PyCQA/pycodestyle/issues/373
     "F811", # support typing.overload decorator
     "F722", # allow Annotated[typ, some_func("some string")]
+    "E701", # See: https://black.readthedocs.io/en/latest/guides/using_black_with_other_tools.html#e701-e704
 ]
 max-line-length = 88 # Respect black's line length (default 88),
 exclude = [".tox", "venv"]
@@ -113,8 +114,8 @@ skipsdist=True
 # Don't create a virtualenv for the command, requires tox-direct plugin
 direct = True
 passenv = *
-allowlist_externals = 
-    pytest 
+allowlist_externals =
+    pytest
     pre-commit
     mypy
     sphinx-build