See if double-quotes are the problem

Double-quotes are used in the Mergeable JSON so perhaps they're not being properly escaped

.github/mergeable.yml

@@ -9,10 +9,10 @@ mergeable:
           - and:
             - must_include:
                 regex: 'release notes: yes'
-                message: 'Please add the label "release notes: yes"'
+                message: 'Please add the label **release notes: yes**'
             - must_include:
                 regex: '^lang\/'
-                message: 'Please add a language ("lang/*") label'
+                message: 'Please add a language label **(lang/...)**'
           - must_include:
               regex: 'release notes: no'
-              message: 'Please add the label "release notes: no"'
+              message: 'Please add the label **release notes: no**'