patchtest: Add tests from patchtest oe repo

Copy the core components of the patchtest-oe repo into
meta/lib/patchtest in oe-core.

(From OE-Core rev: 257f64f4e4414b78981104aec132b067beb5a92a)

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/patchtest/tests/test_mbox_description.py

@@ -0,0 +1,17 @@
+# Checks related to the patch's commit_message
+#
+# Copyright (C) 2016 Intel Corporation
+#
+# SPDX-License-Identifier: GPL-2.0
+
+import base
+
+class CommitMessage(base.Base):
+
+    def test_commit_message_presence(self):
+        for commit in CommitMessage.commits:
+            if not commit.commit_message.strip():
+                self.fail('Patch is missing a descriptive commit message',
+                          'Please include a commit message on your patch explaining the change (most importantly why the change is being made)',
+                          commit)
+