There are several places in the source code where
HTTP response codes are used as numeric values.
These values are used from six.moves and the
numeric values are replaced by constants.
All of the used status codes were replaced with symbolic constants
from six.moves.http_client. More about six.moves.http_client can be
found at [2], under the table "Supported renames:".
Also, this change improves code readibility.
This patchset does not extract numeric values
from the tests, but it can be found at [1].
[1]: Idfc7b043552f428f01ac3e47b270ee0639a8f5bc
[2]: https://pythonhosted.org/six/#module-six.moves
Change-Id: Ib9e26dcea927e96e65c626c18421621d3a29a64d
Partial-Bug: #1520159
8a63622348