[entities] Handle cases where dataset maintainer is not a CWUser

entities.py

@@ -106,9 +106,12 @@ class CKANDatasetAdapter(EntityAdapter):
                }
         maintainer = self.dataset_maintainer()
         if maintainer:
-            data['maintainer'] = maintainer.dc_long_title()
-            if maintainer.primary_email:
-                data['maintainer_email'] = maintainer.primary_email[0].address
+            if isinstance(maintainer, basestring):
+                data['maintainer'] = maintainer
+            else:
+                data['maintainer'] = maintainer.dc_long_title()
+                if maintainer.primary_email:
+                    data['maintainer_email'] = maintainer.primary_email[0].address
         data['tags'] = list(self.dataset_tags())
         data['extras'] = list(self.dataset_extras())
         return data