repo_pull: Handle abnormal responses

urllib.error.HTTPError works as a http response object (same type that
urlopen() returns). Handle the exception by reading and parsing the
response body of the error.

Test: ./repo_review.py --add-reviewer [invalid username] [query]
Test: ./repo_review.py --add-reviewer [ambiguous username] [query]
Change-Id: Ibfc261d83f2f9efd7873835f74ce8d5e980821c9
1 file changed