Make user_id required and add post tests

- raise an exception in ApplicationRoles.get()
- permission_sets is not changed if bad data is sent

atst/domain/application_roles.py

@@ -1,6 +1,9 @@
+from sqlalchemy.orm.exc import NoResultFound
+
 from atst.database import db
 from atst.models import ApplicationRole, ApplicationRoleStatus
-from atst.domain.permission_sets import PermissionSets
+from .permission_sets import PermissionSets
+from .exceptions import NotFoundError
 
 
 class ApplicationRoles(object):
@@ -31,13 +34,16 @@ class ApplicationRoles(object):
 
     @classmethod
     def get(cls, user_id, application_id):
-        existing_app_role = (
-            db.session.query(ApplicationRole)
-            .filter_by(user_id=user_id, application_id=application_id)
-            .one_or_none()
-        )
+        try:
+            app_role = (
+                db.session.query(ApplicationRole)
+                .filter_by(user_id=user_id, application_id=application_id)
+                .one()
+            )
+        except NoResultFound:
+            raise NotFoundError("application_role")
 
-        return existing_app_role
+        return app_role
 
     @classmethod
     def update_permission_sets(cls, application_role, new_perm_sets_names):