Fix Python 3 issues in cmd

* Replace filter() with a list-comprehension using if to get a list on
  Python 3.
* Get the mock module from the stdlib unittest module on Python 3.3 and
  newer, or fallback to the third-party mock module.
* Replace __builtin__ with six.moves.builtins.
* tox.ini: add the following tests for Python 3.4

  - cinder.tests.unit.test_api
  - cinder.tests.unit.test_cmd

Blueprint cinder-python3
Change-Id: Iea516ae598e8eebfc1087663a9b3e0a00d0633d3

cinder/cmd/rtstool.py

@@ -229,7 +229,7 @@ def parse_optional_create(argv):
 
     for arg in argv:
         if arg.startswith('-a'):
-            ips = filter(None, arg[2:].split(','))
+            ips = [ip for ip in arg[2:].split(',') if ip]
             if not ips:
                 usage()
             optional_args['portals_ips'] = ips

cinder/tests/unit/test_cmd.py

@@ -14,7 +14,10 @@ import datetime
 import six
 import sys
 
-import mock
+try:
+    from unittest import mock
+except ImportError:
+    import mock
 from oslo_config import cfg
 
 try:
@@ -533,7 +536,7 @@ class TestCinderManageCmd(test.TestCase):
 
             self.assertEqual(expected_out, fake_out.getvalue())
 
-    @mock.patch('__builtin__.open')
+    @mock.patch('six.moves.builtins.open')
     @mock.patch('os.listdir')
     def test_get_log_commands_errors(self, listdir, open):
         CONF.set_override('log_dir', 'fake-dir')
@@ -552,7 +555,7 @@ class TestCinderManageCmd(test.TestCase):
             open.assert_called_once_with('fake-dir/fake-error.log', 'r')
             listdir.assert_called_once_with(CONF.log_dir)
 
-    @mock.patch('__builtin__.open')
+    @mock.patch('six.moves.builtins.open')
     @mock.patch('os.path.exists')
     def test_get_log_commands_syslog_no_log_file(self, path_exists, open):
         path_exists.return_value = False

tox.ini

@@ -35,6 +35,7 @@ commands =
     cinder.tests.unit.targets.test_lio_driver \
     cinder.tests.unit.targets.test_scst_driver \
     cinder.tests.unit.targets.test_tgt_driver \
+    cinder.tests.unit.test_api \
     cinder.tests.unit.test_api_urlmap \
     cinder.tests.unit.test_backup \
     cinder.tests.unit.test_backup_ceph \
@@ -44,6 +45,7 @@ commands =
     cinder.tests.unit.test_block_device \
     cinder.tests.unit.test_blockbridge \
     cinder.tests.unit.test_cloudbyte \
+    cinder.tests.unit.test_cmd \
     cinder.tests.unit.test_conf \
     cinder.tests.unit.test_context \
     cinder.tests.unit.test_create_volume_flow \