Use python abc in auth class

Instead of using NotImplementedError the abc class has the advantage
that it fails faster if a class doesn't implement the needed interface.
Adapt unit test and test class.

Change-Id: Ide914a4bb577a28a3d202cbf088c404323a29b21
Partial-Bug: #1346797

tempest/auth.py

@@ -13,10 +13,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import abc
 import copy
 import datetime
 import exceptions
 import re
+import six
 import urlparse
 
 from tempest import config
@@ -31,6 +33,7 @@ CONF = config.CONF
 LOG = logging.getLogger(__name__)
 
 
+@six.add_metaclass(abc.ABCMeta)
 class AuthProvider(object):
     """
     Provide authentication
@@ -70,18 +73,21 @@ class AuthProvider(object):
                    interface=self.interface, cache=self.cache
                )
 
+    @abc.abstractmethod
     def _decorate_request(self, filters, method, url, headers=None, body=None,
                           auth_data=None):
         """
         Decorate request with authentication data
         """
-        raise NotImplementedError
+        return
 
+    @abc.abstractmethod
     def _get_auth(self):
-        raise NotImplementedError
+        return
 
+    @abc.abstractmethod
     def _fill_credentials(self, auth_data_body):
-        raise NotImplementedError
+        return
 
     def fill_credentials(self):
         """
@@ -130,8 +136,9 @@ class AuthProvider(object):
         self.cache = None
         self.credentials.reset()
 
+    @abc.abstractmethod
     def is_expired(self, auth_data):
-        raise NotImplementedError
+        return
 
     def auth_request(self, method, url, headers=None, body=None, filters=None):
         """
@@ -188,11 +195,12 @@ class AuthProvider(object):
         self.alt_part = request_part
         self.alt_auth_data = auth_data
 
+    @abc.abstractmethod
     def base_url(self, filters, auth_data=None):
         """
         Extracts the base_url based on provided filters
         """
-        raise NotImplementedError
+        return
 
 
 class KeystoneAuthProvider(AuthProvider):
@@ -225,11 +233,13 @@ class KeystoneAuthProvider(AuthProvider):
         # no change to method or body
         return str(_url), _headers, body
 
+    @abc.abstractmethod
     def _auth_client(self):
-        raise NotImplementedError
+        return
 
+    @abc.abstractmethod
     def _auth_params(self):
-        raise NotImplementedError
+        return
 
     def _get_auth(self):
         # Bypasses the cache

tempest/tests/test_auth.py

@@ -59,12 +59,24 @@ class TestBaseAuthProvider(BaseAuthTestsSetUp):
     obviously don't test not implemented method or the ones which strongly
     depends on them.
     """
-    _auth_provider_class = auth.AuthProvider
 
-    def test_check_credentials_class(self):
-        self.assertRaises(NotImplementedError,
-                          self.auth_provider.check_credentials,
-                          auth.Credentials())
+    class FakeAuthProviderImpl(auth.AuthProvider):
+        def _decorate_request():
+            pass
+
+        def _fill_credentials():
+            pass
+
+        def _get_auth():
+            pass
+
+        def base_url():
+            pass
+
+        def is_expired():
+            pass
+
+    _auth_provider_class = FakeAuthProviderImpl
 
     def test_check_credentials_bad_type(self):
         self.assertFalse(self.auth_provider.check_credentials([]))
@@ -74,16 +86,6 @@ class TestBaseAuthProvider(BaseAuthTestsSetUp):
         auth_provider = self._auth(credentials={})
         self.assertIsInstance(auth_provider.credentials, auth.Credentials)
 
-    def test_instantiate_with_bad_credentials_type(self):
-        """
-        Assure that credentials with bad type fail with TypeError
-        """
-        self.assertRaises(TypeError, self._auth, [])
-
-    def test_auth_data_property(self):
-        self.assertRaises(NotImplementedError, getattr, self.auth_provider,
-                          'auth_data')
-
     def test_auth_data_property_when_cache_exists(self):
         self.auth_provider.cache = 'foo'
         self.useFixture(mockpatch.PatchObject(self.auth_provider,
@@ -110,9 +112,10 @@ class TestBaseAuthProvider(BaseAuthTestsSetUp):
         self.assertIsNone(self.auth_provider.alt_part)
         self.assertIsNone(self.auth_provider.alt_auth_data)
 
-    def test_fill_credentials(self):
-        self.assertRaises(NotImplementedError,
-                          self.auth_provider.fill_credentials)
+    def test_auth_class(self):
+        self.assertRaises(TypeError,
+                          auth.AuthProvider,
+                          fake_credentials.FakeCredentials)
 
 
 class TestKeystoneV2AuthProvider(BaseAuthTestsSetUp):