Remove usage of TestCase.skip() method

It is deprecated since version 1.9.0 of testtools.
Instead of this deprecated method skipTest() is now used.

Change-Id: I7b6bbdbf43e7f428d5b3873a07fba7e6d629fa82

neutron/tests/common/helpers.py

@@ -236,8 +236,8 @@ def skip_if_ovs_older_than(ovs_version):
             current_ovs_version = version.StrictVersion(
                 ovs.config['ovs_version'])
             if current_ovs_version < version.StrictVersion(ovs_version):
-                test.skip("This test requires OVS version %s or higher." %
-                          ovs_version)
+                test.skipTest("This test requires OVS version %s or higher." %
+                              ovs_version)
             return f(test)
         return check_ovs_and_skip
     return skip_if_bad_ovs

neutron/tests/fullstack/test_dhcp_agent.py

@@ -107,7 +107,7 @@ class TestDhcpAgentNoHA(BaseDhcpAgentTest):
         # testing matters.
         # TODO(jlibosva) revisit when ip_lib supports nested namespaces
         if self.environment.hosts[0].dhcp_agent.namespace is not None:
-            self.skip("ip_lib doesn't support nested namespaces")
+            self.skipTest("ip_lib doesn't support nested namespaces")
 
         self.vm.block_until_dhcp_config_done()
 

neutron/tests/unit/testlib_api.py

@@ -323,7 +323,7 @@ class OpportunisticDBTestMixin(object):
         if not hasattr(self, 'db'):
             msg = "backend '%s' unavailable" % self.DRIVER
             if self.SKIP_ON_UNAVAILABLE_DB:
-                self.skip(msg)
+                self.skipTest(msg)
             else:
                 self.fail(msg)