repo-review: Fix missing imports

Bug: None
Test: ./repo_review.py -g [gerrit] query -l Code-Review +2
Change-Id: Iafac171193299ec3894f9674df08cbdcc213af8b

tools/repo_pull/gerrit.py

@@ -25,9 +25,11 @@ import os
 import sys
 
 try:
-    from urllib.request import HTTPBasicAuthHandler, build_opener  # PY3
+    from urllib.request import (
+        HTTPBasicAuthHandler, Request, build_opener)  # PY3
 except ImportError:
-    from urllib2 import HTTPBasicAuthHandler, build_opener  # PY2
+    from urllib2 import (
+        HTTPBasicAuthHandler, Request, build_opener)  # PY2
 
 try:
     from urllib.parse import urlencode, urlparse  # PY3

tools/repo_pull/repo_review.py

@@ -22,6 +22,11 @@ from __future__ import print_function
 
 from gerrit import create_url_opener_from_args, query_change_lists, set_review
 
+try:
+    from urllib.error import HTTPError  # PY3
+except ImportError:
+    from urllib2 import HTTPError  # PY2
+
 import argparse
 import json
 import os