Convert sanity tests to plugins. (#28425)

* Move sanity into directory.
* Omit abstract classes from returned subclass list.
* Split sanity tests out into plugins.
* Fix abstract class handling for Python 3.

test/runner/lib/sanity/sanity_docs.py

@@ -0,0 +1,44 @@
+"""Sanity test for documentation of sanity tests."""
+from __future__ import absolute_import, print_function
+
+import os
+
+from lib.sanity import (
+    SanitySingleVersion,
+    SanityMessage,
+    SanityFailure,
+    SanitySuccess,
+    sanity_get_tests,
+)
+
+from lib.config import (
+    SanityConfig,
+)
+
+
+class SanityDocsTest(SanitySingleVersion):
+    """Sanity test for documentation of sanity tests."""
+    # noinspection PyUnusedLocal
+    def test(self, args, targets):  # pylint: disable=locally-disabled, unused-argument
+        """
+        :type args: SanityConfig
+        :type targets: SanityTargets
+        :rtype: SanityResult
+        """
+        sanity_dir = 'docs/docsite/rst/dev_guide/testing/sanity'
+        sanity_docs = set(part[0] for part in (os.path.splitext(name) for name in os.listdir(sanity_dir)) if part[1] == '.rst')
+        sanity_tests = set(sanity_test.name for sanity_test in sanity_get_tests())
+
+        missing = sanity_tests - sanity_docs
+
+        results = []
+
+        results += [SanityMessage(
+            message='missing docs for ansible-test sanity --test %s' % r,
+            path=os.path.join(sanity_dir, '%s.rst' % r),
+        ) for r in sorted(missing)]
+
+        if results:
+            return SanityFailure(self.name, messages=results)
+
+        return SanitySuccess(self.name)