Improve missing/not found mkdocs.yml file

Closes #7707

Author: humitos

readthedocs/notifications/messages.py

@@ -448,7 +448,8 @@ def get_rendered_body(self):
             textwrap.dedent(
                 """
             The configuration file for MkDocs was not found.
-            Make sure you have a <code>mkdocs.yml</code> file in your repository.
+            Make sure the <code>mkdocs.configuration</code> config is correct,
+            and you have the <code>mkdocs.yml</code> in that location.
             """
             ).strip(),
         ),