Bug 1360498 - Added update snippet URL to failure in case of network issue r=whimboo

MozReview-Commit-ID: Hs9DR7z8aGS

--HG--
extra : rebase_source : a4e294ecdb0f3ac645a0bf1b31c8b510ee66332b

testing/marionette/puppeteer/firefox/firefox_puppeteer/api/software_update.py

@@ -366,7 +366,8 @@ class SoftwareUpdate(BaseLib):
             return response.read()
         except urllib2.URLError:
             exc, val, tb = sys.exc_info()
-            raise Exception, "Failed to retrieve update snippet: {}".format(val), tb
+            raise Exception, "Failed to retrieve update snippet '{}': {}".format(
+                update_url, val), tb
 
     def get_formatted_update_url(self, force=False):
         """Retrieve the formatted AUS update URL the update snippet is retrieved from.