Fix issues with newer flake8

The updated flake8 seems to have fixed a check for .format() issues that
discovered a bug in one of our tests, which is fixed here.

Also get rid of using "l" as a variable name and tag the imports that
need to stay in order after setting an environment variable.

Change-Id: I28de0ffa68f9bff4685d81fe7b5a5d8909e2313c

designate/__init__.py

@@ -19,9 +19,9 @@ import os
 # the /etc/hosts file, causing problems for installs.
 os.environ['EVENTLET_NO_GREENDNS'] = 'yes'  # noqa
 
-from oslo_log import log
-from oslo_concurrency import lockutils
-import oslo_messaging as messaging
+from oslo_log import log  # noqa
+from oslo_concurrency import lockutils  # noqa
+import oslo_messaging as messaging  # noqa
 
 _EXTRA_DEFAULT_LOG_LEVELS = [
     'kazoo.client=WARN',

designate/tests/unit/test_central/test_basic.py

@@ -458,7 +458,7 @@ class CentralServiceTestCase(CentralBasic):
         #  we will hit it if we try to do the operations in a loop 100 times.
         for num in range(100):
             recordset = Mock()
-            recordset.name = "b%s".format(num)
+            recordset.name = "b{}".format(num)
             recordset.obj_attr_is_set.return_value = True
             recordset.records = [MockRecord()]
 

devstack/networking_test.py

@@ -61,10 +61,10 @@ designate_cli_path = '/usr/local/bin/designate'
 openstack_cli = 'openstack'
 
 
-def gen_random_name(l):
+def gen_random_name(length):
     return "".join(
         random.choice(string.ascii_lowercase + string.digits)
-        for n in range(l)
+        for n in range(length)
     )