Bug 1606009 - Extend the yaml test r=Callek

Differential Revision: https://phabricator.services.mozilla.com/D58265

--HG--
extra : moz-landing-system : lando

tools/lint/test/files/yaml/bad.yml

@@ -5,3 +5,4 @@ yamllint:
         - .cron.yml
         - browser/config/
         - wrong
+  application:bar

tools/lint/test/test_yaml.py

@@ -9,7 +9,7 @@ pytestmark = pytest.mark.skipif(not which('yamllint'), reason="yamllint is not i
 def test_basic(lint, paths):
     results = lint(paths())
 
-    assert len(results) == 2
+    assert len(results) == 3
 
     assert "line too long (122 > 80 characters)" in results[0].message
     assert results[0].level == "error"
@@ -21,6 +21,11 @@ def test_basic(lint, paths):
     assert "bad.yml" in results[1].relpath
     assert results[0].lineno == 3
 
+    assert "could not find expected" in results[2].message
+    assert results[2].level == "error"
+    assert "bad.yml" in results[2].relpath
+    assert results[2].lineno == 9
+
 
 if __name__ == '__main__':
     mozunit.main()