Make the kerberos plugin loadable

This patch adds a BaseLoader class for the Kerberos plugin and an entry
point in setup.cfg.

Since the plugin file is being renamed, also fix the comment that
refers to the library as 'keystoneauth' - it is called 'keystoneauth1'
and trying to install 'keystoneauth' will cause the outdated version of
the library to be installed and kerberos will not work.

To make sure the plugin was loadable, this was tested using a version
of python-openstackclient that had been migrated to keystoneauth[1].

[1] https://review.openstack.org/#/c/276350/

Change-Id: Id339295c795f6bf1b428dac8fc9f79d2f5fb453f
Closes-bug: #1567257
Partial-bug: #1567260

keystoneauth1/extras/kerberos/__init__.py

@@ -18,11 +18,13 @@
     not installed by default. Without the extra package an import error will
     occur. The extra package can be installed using::
 
-      $ pip install keystoneauth['kerberos']
-
+      $ pip install keystoneauth1[kerberos]
 """
 
-import requests_kerberos
+try:
+    import requests_kerberos
+except ImportError:
+    requests_kerberos = None
 
 from keystoneauth1 import access
 from keystoneauth1.identity import v3
@@ -37,10 +39,24 @@ def _requests_auth():
         mutual_authentication=requests_kerberos.OPTIONAL)
 
 
+def _dependency_check():
+    if requests_kerberos is None:
+        raise ImportError("""
+Using the kerberos authentication plugin requires installation of additional
+packages. These can be installed with::
+
+    $ pip install keystoneauth1[kerberos]
+""")
+
+
 class KerberosMethod(v3.AuthMethod):
 
     _method_parameters = []
 
+    def __init__(self, *args, **kwargs):
+        _dependency_check()
+        super(KerberosMethod, self).__init__(*args, **kwargs)
+
     def get_auth_data(self, session, auth, headers, request_kwargs, **kwargs):
         # NOTE(jamielennox): request_kwargs is passed as a kwarg however it is
         # required and always present when called from keystoneclient.
@@ -59,6 +75,10 @@ class MappedKerberos(federation.FederationBaseAuth):
     use the standard keystone auth process to scope that to any given project.
     """
 
+    def __init__(self, *args, **kwargs):
+        _dependency_check()
+        super(MappedKerberos, self).__init__(*args, **kwargs)
+
     def get_unscoped_auth_ref(self, session, **kwargs):
         resp = session.get(self.federated_token_url,
                            requests_auth=_requests_auth(),

keystoneauth1/extras/kerberos/_loading.py

@@ -0,0 +1,25 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from keystoneauth1.extras import kerberos
+from keystoneauth1 import loading
+
+
+class Kerberos(loading.BaseV3Loader):
+
+    @property
+    def plugin_class(self):
+        return kerberos.Kerberos
+
+    @property
+    def available(self):
+        return kerberos.kerberos_requests is not None

keystoneauth1/tests/unit/extras/kerberos/test_kerberos_loading.py

@@ -0,0 +1,33 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from keystoneauth1 import loading
+from keystoneauth1.tests.unit import utils as test_utils
+
+
+class KerberosLoadingTests(test_utils.TestCase):
+
+    def test_options(self):
+        opts = [o.name for o in
+                loading.get_plugin_loader('v3kerberos').get_options()]
+
+        allowed_opts = ['domain-id',
+                        'domain-name',
+                        'project-id',
+                        'project-name',
+                        'project-domain-id',
+                        'project-domain-name',
+                        'trust-id',
+                        'auth-url',
+                        ]
+
+        self.assertItemsEqual(allowed_opts, opts)

keystoneauth1/tests/unit/extras/kerberos/test_mapped.py

@@ -12,29 +12,16 @@
 
 import uuid
 
-import six
-
+from keystoneauth1.extras import kerberos
 from keystoneauth1 import fixture as ks_fixture
 from keystoneauth1 import session
 from keystoneauth1.tests.unit.extras.kerberos import base
 
-try:
-    # Until requests_kerberos gets py3 support, this is going to fail to import
-    from keystoneauth1.extras import kerberos
-
-except ImportError:
-    if six.PY2:
-        # requests_kerberos is expected to be there on py2, so don't ignore.
-        raise
-
-    # requests_kerberos isn't available
-    kerberos = False
-
 
 class TestMappedAuth(base.TestCase):
 
     def setUp(self):
-        if not kerberos:
+        if kerberos.requests_kerberos is None:
             self.skipTest("Kerberos support isn't available.")
 
         super(TestMappedAuth, self).setUp()

keystoneauth1/tests/unit/extras/kerberos/test_v3.py

@@ -10,29 +10,15 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-
-import six
-
+from keystoneauth1.extras import kerberos
 from keystoneauth1 import session
 from keystoneauth1.tests.unit.extras.kerberos import base
 
-try:
-    # Until requests_kerberos gets py3 support, this is going to fail to import
-    from keystoneauth1.extras import kerberos
-
-except ImportError:
-    if six.PY2:
-        # requests_kerberos is expected to be there on py2, so don't ignore.
-        raise
-
-    # requests_kerberos isn't available
-    kerberos = None
-
 
 class TestKerberosAuth(base.TestCase):
 
     def setUp(self):
-        if not kerberos:
+        if kerberos.requests_kerberos is None:
             self.skipTest("Kerberos support isn't available.")
 
         super(TestKerberosAuth, self).setUp()

keystoneauth1/tests/unit/extras/kerberos/utils.py

@@ -36,6 +36,9 @@ class KerberosMock(fixtures.Fixture):
     def setUp(self):
         super(KerberosMock, self).setUp()
 
+        if requests_kerberos is None:
+            return
+
         m = mockpatch.PatchObject(requests_kerberos.HTTPKerberosAuth,
                                   'generate_request_header',
                                   self._generate_request_header)

setup.cfg

@@ -48,6 +48,7 @@ keystoneauth1.plugin =
     v3oidcauthcode = keystoneauth1.loading._plugins.identity.v3:OpenIDConnectAuthorizationCode
     v3oidcaccesstoken = keystoneauth1.loading._plugins.identity.v3:OpenIDConnectAccessToken
     v3oauth1 = keystoneauth1.extras.oauth1._loading:V3OAuth1
+    v3kerberos = keystoneauth1.extras.kerberos._loading:Kerberos
 
 [build_sphinx]
 source-dir = doc/source