Bug 1272176 - Import mozharness to avoid missing symbol; r=me

This fixes a bug in 901aee13bd76.

testing/mozharness/mozharness/mozilla/testing/talos.py

@@ -14,6 +14,7 @@ import copy
 import re
 import json
 
+import mozharness
 from mozharness.base.config import parse_config_file
 from mozharness.base.errors import PythonErrorList
 from mozharness.base.log import OutputParser, DEBUG, ERROR, CRITICAL