"AuthorizationFailure" after I add/remove the current user in a project

My instructions are like below and I always use ipython to check the instructions are fine:
1. Create a new connection(unscope_token) from keystone client
unscope_conn = keystone_client.Client(username="admin", password="password", auth_url="http://127.0.0.1:5000/v2.0")
unscope_token = unscope_conn.auth_token

2. Create a scope_token from unscope_token
tokens = unscope_conn.tokens.authenticate(token=unscope_token, tenant_name="admin")
scope_token = tokens.id

3. Create a scope connection from scope_token
scope_conn = keystone_client.Client(token=scope_token, endpoint="http://127.0.0.1:35357/v2.0")

4. Add/Remove the current user in a project using the scope connection
user_id = "7345085bf11e47e98273affaf69b5ee6" #This is the user id for "admin"
role_id = "2ad4ede52c8940779f8bb4746d3f44c6" #This is one of the roles in the role list
tenant_id = "b2d0bf5931e949e988a2ce2dbb2ce0fa" #This is one of the projects I created before
scope_conn.add_user_role(user_id, role_id, tenant_id)

5. The user has been added to the project from the step 4. But if I need to use the same scope connection to do other things, I would get an error "AuthorizationFailure"
For example:
scope_conn.roles.list()
Then I would get "AuthorizationFailure: Authorization Failed: maximum recursion depth exceeded while calling a Python object"

My Question is
Is it a limitation if a user add/remove himself in a project, the token must be refresh?