Bug 1361849 - Fix handling of HTTPError when the update snippet cannot be retrieved. r=maja_zf

Re-raising an HTTPError with a modified reason would require 6 parameters
which we do not have at this point. So re-raise a normal Exception instead.

MozReview-Commit-ID: J9ws4IMDy3g

--HG--
extra : rebase_source : 59af3f6fa28ea4a0057419e340ef011abfcf10a2

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

@@ -360,14 +360,13 @@ class SoftwareUpdate(BaseLib):
 
         :param update_url: URL to the update snippet
         """
-        try:
         import urllib2
+        try:
             response = urllib2.urlopen(update_url)
             return response.read()
-        except Exception:
+        except urllib2.URLError:
             exc, val, tb = sys.exc_info()
-
-            raise exc, "Failed to retrieve update snippet: {}".format(val.reason), tb
+            raise Exception, "Failed to retrieve update snippet: {}".format(val), tb
 
     def get_formatted_update_url(self, force=False):
         """Retrieve the formatted AUS update URL the update snippet is retrieved from.