JSON serialization error when listing flows through REST API (OF1.0)

Documenting the issue originally reported by @josemauro and @cmagnobarbosa:

Install Kytos and the flow_manager NApp.
Run mininet: sudo mn --topo linear,3 --mac --controller=remote,ip=127.0.0.1 --switch ovsk,protocols=OpenFlow10

Install a flow

curl --header "Content-Type: application/json" \
--request POST \
--data '{
"flows":[
{
  "priority": 17,
  "idle_timeout":360,
  "hard_timeout":1200,
  "cookie":84114904,
  "match":{
    "in_port":2,
    "dl_src":"00:1f:3a:3e:9a:cf",
    "dl_dst":"00:15:af:d5:38:98",
    "dl_type":2048,
    "dl_vlan":300,
    "dl_vlan_pcp":0,
    "nw_src":"192.168.0.1",
    "nw_dst":"192.168.0.2",
    "nw_proto":17
  },
  "actions":[
    {
      "action_type":"output",
      "port":42
    },
    {
      "action_type":"set_vlan",
      "vlan_id":42
    }
  ]
}
]
}' \
http://127.0.0.1:8181/api/kytos/flow_manager/v2/flows/00:00:00:00:00:00:00:01

If the step above fails because the switch is disabled, enable it in the kytos console: kytos $> controller.switches['00:00:00:00:00:00:00:01'].enable()
List flows through the REST API: curl http://127.0.0.1:8181/api/kytos/flow_manager/v2/flows

2020-11-26 18:41:18,413 - ERROR [kytos.core.controller] (Thread-933) Exception on /api/kytos/flow_manager/v2/flows [GET]
Traceback (most recent call last):
  File "venv/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "venv/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "venv/lib/python3.8/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "venv/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "venv/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "venv/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "venv/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "venv/var/lib/kytos/napps/kytos/flow_manager/main.py", line 167, in list
    flows_dict = [flow.as_dict() for flow in switch.flows]
  File "venv/var/lib/kytos/napps/kytos/flow_manager/main.py", line 167, in <listcomp>
    flows_dict = [flow.as_dict() for flow in switch.flows]
  File "venv/var/lib/kytos/napps/../napps/kytos/of_core/flow.py", line 122, in as_dict
    flow_dict['id'] = self.id
  File "venv/var/lib/kytos/napps/../napps/kytos/of_core/flow.py", line 94, in id
    flow_str = self.as_json(sort_keys=True, include_id=False)
  File "venv/var/lib/kytos/napps/../napps/kytos/of_core/flow.py", line 167, in as_json
    return json.dumps(self.as_dict(include_id), sort_keys=sort_keys)
  File "/usr/lib/python3.8/json/__init__.py", line 234, in dumps
    return cls(
  File "/usr/lib/python3.8/json/encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python3.8/json/encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "/usr/lib/python3.8/json/encoder.py", line 179, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type UBInt16 is not JSON serializable

kytos / flow_manager

JSON serialization error when listing flows through REST API (OF1.0) #97