Add mccabe complexity testing (#64623)

* Add mccabe complexity testing

* Make mccabe complexity an optional error

* Add mccabe to new sanity pylint requirements

* Add a changelog fragment.

Co-authored-by: Matt Clay <matt@mystile.com>

changelogs/fragments/ansible-test-pytest-mccabe.yml

@@ -0,0 +1,2 @@
+minor_changes:
+    - ansible-test now includes the ``pylint`` plugin ``mccabe`` in optional sanity tests enabled with ``--enable-optional-errors``

test/lib/ansible_test/_data/requirements/sanity.pylint.txt

@@ -1,2 +1,3 @@
 pylint ; python_version < '3.9'  # installation fails on python 3.9.0b1
 pyyaml  # needed for collection_detail.py
+mccabe  # pylint complexity testing

test/lib/ansible_test/_internal/sanity/pylint.py

@@ -56,6 +56,7 @@ class PylintTest(SanitySingleVersion):
         super(PylintTest, self).__init__()
         self.optional_error_codes.update([
             'ansible-deprecated-date',
+            'too-complex',
         ])
 
     @property
@@ -225,7 +226,7 @@ class PylintTest(SanitySingleVersion):
             config = dict()
 
         disable_plugins = set(i.strip() for i in config.get('disable-plugins', '').split(',') if i)
-        load_plugins = set(plugin_names) - disable_plugins
+        load_plugins = set(plugin_names + ['pylint.extensions.mccabe']) - disable_plugins
 
         cmd = [
             python,
@@ -233,6 +234,7 @@ class PylintTest(SanitySingleVersion):
             '--jobs', '0',
             '--reports', 'n',
             '--max-line-length', '160',
+            '--max-complexity', '20',
             '--rcfile', rcfile,
             '--output-format', 'json',
             '--load-plugins', ','.join(load_plugins),