Allow identity provider to be created with remote_ids set to None

When support was added for multiple remote_ids, identity provider
creation was broken when remote_ids are specified as None instead
of an empty list.  The remote_ids are supposed to be optional.  This
causes 400 errors when using python-openstackclient to create an
identity provider without any remote_ids.

Change-Id: I9a4d1206f6df95636ae350236f6e704ca37f7b73
Closes-bug: #1440185

keystone/contrib/federation/backends/sql.py

@@ -58,7 +58,9 @@ class IdentityProviderModel(sql.ModelBase, sql.DictBase):
     @classmethod
     def from_dict(cls, dictionary):
         new_dictionary = dictionary.copy()
-        remote_ids_list = new_dictionary.pop('remote_ids', [])
+        remote_ids_list = new_dictionary.pop('remote_ids', None)
+        if not remote_ids_list:
+            remote_ids_list = []
         identity_provider = cls(**new_dictionary)
         remote_ids = []
         # NOTE(fmarco76): the remote_ids_list contains only remote ids

keystone/tests/unit/test_v3_federation.py

@@ -856,6 +856,21 @@ class FederatedIdentityProviderTests(FederationTests):
                                  keys_to_check=keys_to_check,
                                  ref=body)
 
+    def test_create_idp_remote_none(self):
+        """Creates an IdP with a None remote_ids."""
+
+        keys_to_check = list(self.idp_keys)
+        keys_to_check.append('remote_ids')
+        body = self.default_body.copy()
+        body['description'] = uuid.uuid4().hex
+        body['remote_ids'] = None
+        resp = self._create_default_idp(body=body)
+        expected = body.copy()
+        expected['remote_ids'] = []
+        self.assertValidResponse(resp, 'identity_provider', dummy_validator,
+                                 keys_to_check=keys_to_check,
+                                 ref=expected)
+
     def test_update_idp_remote_ids(self):
         """Update IdP's remote_ids parameter."""
         body = self.default_body.copy()