Add exception to mypy.ini

Author: abravalheri

mypy.ini

@@ -34,3 +34,8 @@ ignore_missing_imports = True
 # - setuptools._vendor.packaging._manylinux: Mypy issue, this vendored module is already excluded!
 [mypy-pkg_resources.tests.*,setuptools._vendor.packaging._manylinux,setuptools.config._validate_pyproject.*]
 disable_error_code = import-not-found
+
+# - The unused-ignore comment in setuptools.config._validate_pyproject.* is probably evaluated differently
+#   in different versions of Python. Also, this file should already be ignored...
+[mypy-setuptools.config._validate_pyproject.*]
+disable_error_code = unused-ignore