Use unittest.mock instead of mock

The mock third party library was needed for mock support in py2
runtimes. Since we now only support py36 and later, we can use the
standard lib unittest.mock module instead.

Also added and enabled a hacking check that would have caught this.

Change-Id: Idb10f84fd32c50db24f844352cb85de452181439

lower-constraints.txt

@@ -64,7 +64,6 @@ logutils==0.3.5
 Mako==1.0.7
 MarkupSafe==1.0
 mccabe==0.4.0
-mock==2.0.0
 monotonic==1.4
 mox3==0.25.0
 msgpack==0.5.6

octavia/hacking/checks.py

@@ -66,6 +66,8 @@ untranslated_exception_re = re.compile(r"raise (?:\w*)\((.*)\)")
 no_eventlet_re = re.compile(r'(import|from)\s+[(]?eventlet')
 no_line_continuation_backslash_re = re.compile(r'.*(\\)\n')
 no_logging_re = re.compile(r'(import|from)\s+[(]?logging')
+import_mock_re = re.compile(r"\bimport[\s]+mock\b")
+import_from_mock_re = re.compile(r"\bfrom[\s]+mock[\s]+import\b")
 
 
 def _translation_checks_not_enforced(filename):
@@ -258,3 +260,18 @@ def check_no_logging_imports(logical_line):
     if no_logging_re.match(logical_line):
         msg = 'O348 Usage of Python logging module not allowed, use oslo_log'
         yield logical_line.index('logging'), msg
+
+
+@core.flake8ext
+def check_no_import_mock(logical_line):
+    """O349 - Test code must not import mock library.
+
+    :param logical_line: The logical line to check.
+    :returns: None if the logical line passes the check, otherwise a tuple
+              is yielded that contains the offending index in logical line
+              and a message describe the check validation failure.
+    """
+    if (import_mock_re.match(logical_line) or
+            import_from_mock_re.match(logical_line)):
+        msg = 'O349 Test code must not import mock library, use unittest.mock'
+        yield 0, msg

octavia/tests/unit/api/drivers/driver_agent/test_driver_updater.py

@@ -13,13 +13,13 @@
 #    under the License.
 import copy
 from unittest import mock
+from unittest.mock import call
 
-from mock import call
+from octavia_lib.api.drivers import exceptions as driver_exceptions
+from octavia_lib.common import constants as lib_consts
 
 from octavia.api.drivers.driver_agent import driver_updater
 import octavia.tests.unit.base as base
-from octavia_lib.api.drivers import exceptions as driver_exceptions
-from octavia_lib.common import constants as lib_consts
 
 
 class TestDriverUpdater(base.TestCase):

tox.ini

@@ -190,6 +190,7 @@ extension =
   O346 = checks:check_line_continuation_no_backslash
   O347 = checks:revert_must_have_kwargs
   O348 = checks:check_no_logging_imports
+  O349 = checks:check_no_import_mock
 paths =
   ./octavia/hacking