Add pep8 import order validation

Add the flake8-import-order library to our test requirements so that we
can avoid these PEP8 violations and maintain consistent import ordering.
Also fix our violations.

This library is in requirements but is blacklisted from being
automatically updated since it is never shipped. For now, don't bother
to pin it.

Change-Id: I4e788292b98b7f2f835cc80081763b2d249fe43e

keystoneauth1/identity/v3/tokenless_auth.py

@@ -11,6 +11,7 @@
 # under the License.
 
 import abc
+
 import six
 
 from keystoneauth1 import _utils as utils

keystoneauth1/tests/unit/access/test_v3_access.py

@@ -10,9 +10,9 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import datetime
 import uuid
 
-import datetime
 from oslo_utils import timeutils
 
 from keystoneauth1 import access

keystoneauth1/tests/unit/test_betamax_fixture.py

@@ -10,11 +10,10 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import testtools
-
 import betamax
 from betamax import exceptions
 import mock
+import testtools
 
 from keystoneauth1.fixture import keystoneauth_betamax
 from keystoneauth1.fixture import serializer

keystoneauth1/tests/unit/test_betamax_hooks.py

@@ -10,8 +10,9 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import betamax
 import json
+
+import betamax
 import mock
 from requests import models
 import testtools

keystoneauth1/tests/unit/test_discovery.py

@@ -11,9 +11,9 @@
 # under the License.
 
 import json
-import mock
 import re
 
+import mock
 from testtools import matchers
 
 from keystoneauth1 import adapter

test-requirements.txt

@@ -4,6 +4,7 @@
 
 hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
 flake8-docstrings==0.2.1.post1 # MIT
+flake8-import-order
 
 bandit>=1.1.0 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0

tox.ini

@@ -61,6 +61,8 @@ ignore = D100,D101,D102,D103,D104,D203
 enable-extensions=H106,H203
 show-source = True
 exclude = .venv,.tox,dist,doc,*egg,build
+import-order-style = pep8
+application-import-names = keystoneauth1
 
 [testenv:docs]
 deps = -r{toxinidir}/doc/requirements.txt