api = API(
    api_root_url='...api_url...',
    params={},
    headers={
        'Authorization': 'Bearer [...]')
    },
    timeout=30,
    append_slash=False,
    json_encode_body=True,
)
api.add_resource(resource_name='projects')
api.projects.actions # runs ok!
api.projects.list() # Failure!

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/simple_rest_client/resource.py", line 101, in action_method
    return make_request(self.client, request)
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/simple_rest_client/decorators.py", line 35, in wrapper
    response = f(*args, **kwargs)
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/simple_rest_client/request.py", line 25, in make_request
    client_response = client_method(request.url, **client_options)
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/httpx/_client.py", line 804, in get
    return self.request(
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/httpx/_client.py", line 640, in request
    return self.send(
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/httpx/_client.py", line 670, in send
    response = self._send_handling_redirects(
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/httpx/_client.py", line 699, in _send_handling_redirects
    response = self._send_handling_auth(
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/httpx/_client.py", line 736, in _send_handling_auth
    response = self._send_single_request(request, timeout)
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/httpx/_client.py", line 759, in _send_single_request
    (
  File "/usr/local/anaconda3/envs/test/lib/python3.8/contextlib.py", line 131, in __exit__
    self.gen.throw(type, value, traceback)
  File "/usr/local/anaconda3/envs/test/lib/python3.8/site-packages/httpx/_exceptions.py", line 359, in map_exceptions
    raise mapped_exc(message, **kwargs) from None  # type: ignore
httpx._exceptions.ProxyError: 503 Error