HasLength() rewritten to assertEqual()

HasLength() based assertions are re-written to assertEqual() based
assertion to homogenize the test code base.

For example:

assertThat(.., HasLength()) becomes assertEqual(len(),...)

Change-Id: Ia3bf24e34fffe445ff4b0ee61fb7cbc0eb36a57a
Closes-Bug:#1629898

watcher/tests/objects/test_audit.py

@@ -14,8 +14,6 @@
 #    under the License.
 
 import mock
-from testtools import matchers
-
 from watcher.common import exception
 # from watcher.common import utils as w_utils
 from watcher import objects
@@ -58,7 +56,7 @@ class TestAuditObject(base.DbTestCase):
             mock_get_list.return_value = [self.fake_audit]
             audits = objects.Audit.list(self.context)
             self.assertEqual(1, mock_get_list.call_count, 1)
-            self.assertThat(audits, matchers.HasLength(1))
+            self.assertEqual(1, len(audits))
             self.assertIsInstance(audits[0], objects.Audit)
             self.assertEqual(self.context, audits[0]._context)