Bug 1686706 - Throw error if browsertime can't find any youtube playback results r=perftest-reviewers,sparky

Differential Revision: https://phabricator.services.mozilla.com/D101742

testing/raptor/raptor/output.py

@@ -1552,6 +1552,7 @@ class BrowsertimeOutput(PerftestOutput):
                     subtest["replicates"].extend(replicates)
 
             elif "benchmark" in test["type"]:
+                subtests = None
                 if "speedometer" in test["name"]:
                     subtests, vals = self.parseSpeedometerOutput(test)
                 if "ares6" in test["name"]:
@@ -1563,6 +1564,9 @@ class BrowsertimeOutput(PerftestOutput):
                 if "unity-webgl" in test["name"]:
                     subtests, vals = self.parseUnityWebGLOutput(test)
 
+                if subtests is None:
+                    raise Exception("No benchmark metrics found in browsertime results")
+
                 suite["subtests"] = subtests
                 # summarize results for both benchmark type tests
                 if len(subtests) > 1: