Bug 1125834 - Don't print class name of Marionette exceptions twice. r=automatedtester

MozReview-Commit-ID: 6ctHHB8uDZm

--HG--
extra : rebase_source : 61ef531649b45e77dd3cb8358b635e95c5e82253

testing/marionette/client/marionette_driver/errors.py

@@ -49,7 +49,10 @@ class MarionetteException(Exception):
             st = "".join(["\t%s\n" % x for x in self.stacktrace.splitlines()])
             msg += "\nstacktrace:\n%s" % st
 
-        return "".join(traceback.format_exception(self.__class__, msg, tb)).strip()
+        if tb:
+            msg += ': ' + "".join(traceback.format_tb(tb))
+
+        return msg
 
 
 class ElementNotSelectableException(MarionetteException):

testing/marionette/harness/marionette/tests/unit/test_errors.py

@@ -38,7 +38,6 @@ class TestErrors(marionette_test.MarionetteTestCase):
         self.assertIn(message, r)
         self.assertIn(", caused by %r" % cause[0], r)
         self.assertIn("\nstacktrace:\n\tfirst\n\tsecond", r)
-        self.assertIn("MarionetteException:", r)
 
     def test_cause_string(self):
         exc = errors.MarionetteException(cause="foo")