Bug 1564425 - Improve error handling of mach addtest, r=bgrins

Ensure that if we try to create a mochitest of unsupported file type we return a
useful error

Differential Revision: https://phabricator.services.mozilla.com/D38224

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

testing/addtest.py

@@ -70,12 +70,15 @@ class MochitestCreator(Creator):
         template_file_name = self.templates.get(self.suite)
 
         if template_file_name is None:
+            print("Sorry, `addtest` doesn't currently know how to add {}".format(self.suite))
             return None
 
         template_file_name = template_file_name % {"doc": self.doc}
 
         template_file = os.path.join(mochitest_templates, template_file_name)
         if not os.path.isfile(template_file):
+            print("Sorry, `addtest` doesn't currently know how to add {} with document type {}"
+                  .format(self.suite, self.doc))
             return None
 
         with open(template_file) as f:

testing/mach_commands.py

@@ -193,7 +193,11 @@ class AddTest(MachCommandBase):
         creator.check_args()
 
         paths = []
+        added_tests = False
         for path, template in creator:
+            if not template:
+                continue
+            added_tests = True
             if (path):
                 paths.append(path)
                 print("Adding a test file at {} (suite `{}`)".format(path, suite))
@@ -209,6 +213,9 @@ class AddTest(MachCommandBase):
                 # write to stdout if you passed only suite and doc and not a file path
                 print(template)
 
+        if not added_tests:
+            return 1
+
         if test:
             creator.update_manifest()