Fix bug in scenario/manager and cover it with pep8

manager.py had a syntax error which caused the module to be not
installable.  This wasn't picked up in testing.  This fixes the bug
and adds pep8 coverage to the nova_lxd_tempest_plugin so that the module
always remains installable.

Also, this fixes the tempest concurrency at 1.  See the related bugs.

Closes-bug: #1790956
Related-Bug: #1790943
Change-Id: Ie542b062a9f0997f6363877ff03f0f9bfc8f3d43
(cherry picked from commit c4c16bcf49)

devstack/tempest-dsvm-lxd-rc

@@ -87,3 +87,7 @@ r="$r|(?:.*ServerShowV263Test.test_show_update_rebuild_list_server.*)"
 r="$r).*$"
 
 export DEVSTACK_GATE_TEMPEST_REGEX="$r"
+
+# set the concurrency to 1 for devstack-gate
+# See: https://bugs.launchpad.net/nova-lxd/+bug/1790943
+export TEMPEST_CONCURRENCY=1

nova_lxd_tempest_plugin/tests/scenario/manager.py

@@ -16,10 +16,8 @@
 
 import subprocess
 
-import netaddr
 from oslo_log import log
 from oslo_serialization import jsonutils as json
-from oslo_utils import netutils
 
 from tempest.common import compute
 from tempest.common import image as common_image
@@ -565,7 +563,7 @@ class ScenarioTest(tempest.test.BaseTestCase):
                           ip=ip_address,
                           timeout=timeout,
                           should_succeed=('reachable' if should_succeed
-                                          else 'unreachable'))
+                                          else 'unreachable')))
         result = test_utils.call_until_true(ping, timeout, 1)
         LOG.debug("{caller} finishes ping {ip} in {timeout} sec and the "
                   "ping result is {result}"

nova_lxd_tempest_plugin/tests/scenario/test_volume_ops.py

@@ -14,18 +14,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import time
 
 from oslo_log import log as logging
-import testtools
 
-from tempest.common import waiters
 from tempest import config
 from tempest import exceptions
-from tempest.lib.common.utils import data_utils
 from tempest.lib.common.utils import test_utils
-from tempest.lib import decorators
-from tempest.lib import exceptions as lib_exc
 
 from nova_lxd_tempest_plugin.tests.scenario import manager
 

tox.ini

@@ -41,7 +41,9 @@ commands =
 [testenv:pep8]
 basepython = python3
 deps = {[testenv]deps}
-commands = flake8 {toxinidir}/nova
+commands =
+  flake8 {toxinidir}/nova
+  flake8 {toxinidir}/nova_lxd_tempest_plugin
 
 [testenv:venv]
 basepython = python3