gistfile.diff

reverted:
--- b/testing/mozharness/mozharness/mozilla/buildbot.py
+++ a/testing/mozharness/mozharness/mozilla/buildbot.py
@@ -44,17 +44,17 @@
     TBPL_EXCEPTION: 3,
     TBPL_RETRY: 4,
 }
 TBPL_WORST_LEVEL_TUPLE = (TBPL_RETRY, TBPL_EXCEPTION, TBPL_FAILURE,
                           TBPL_WARNING, TBPL_SUCCESS)
 
 
 class BuildbotMixin(object):
+    buildbot_config = None
-    buildbot_config = {}
     buildbot_properties = {}
     worst_buildbot_status = TBPL_SUCCESS
 
     def read_buildbot_config(self):
         c = self.config
         if not c.get("buildbot_json_path"):
             # If we need to fail out, add postflight_read_buildbot_config()
             self.info("buildbot_json_path is not set.  Skipping...")
diff -u b/testing/mozharness/mozharness/mozilla/l10n/locales.py b/testing/mozharness/mozharness/mozilla/l10n/locales.py
--- b/testing/mozharness/mozharness/mozilla/l10n/locales.py
+++ b/testing/mozharness/mozharness/mozilla/l10n/locales.py
@@ -51,7 +51,8 @@
         # Buildbot property
         if hasattr(self, 'read_buildbot_config'):
             self.read_buildbot_config()
-            locales = self.buildbot_config.get("locales")
+            if self.buildbot_config:
+                locales = self.buildbot_config.get("locales")
             if locales:
                 self.info("Using locales from buildbot: %s" % locales)
                 locales = locales.split()