Bug 1245953 - Use requests for performing HTTP request; r=garndt

requests should *always* be used for performing HTTP requests because it
has a better API *and* has sane security defaults compared to the HTTP
request APIs in the Python standard library. Although, Python 2.7.9+
does have slightly saner defaults in the standard library. I still trust
requests more.

MozReview-Commit-ID: GqohpfYYGBw

testing/taskcluster/mach_commands.py

@@ -152,10 +152,10 @@ def query_vcs_info(repository, revision):
     PushInfo = namedtuple('PushInfo', ['pushid', 'pushdate'])
 
     try:
-        import urllib2
+        import requests
         url = '%s/json-pushes?changeset=%s' % (repository, revision)
         sys.stderr.write("Querying URL for pushdate: %s\n" % url)
-        contents = json.load(urllib2.urlopen(url))
+        contents = requests.get(url).json()
 
         # The contents should be something like:
         # {