Error text on invalid scope is overly verbose

[ScottWeinstein]

Describe the problem.
The error text if your application account doen't have the correct scope is too verbose

> python .\sample.py
Traceback (most recent call last):
  File ".\sample.py", line 14, in <module>
    with GsSession.get(Environment.PROD, CLIENTID, SECRET, scopes=('read_product_data', 'run_analytics')):
  File "C:\Users\scott\AppData\Roaming\Python\Python37\site-packages\gs_quant\context_base.py", line 67, in __enter__
    self._on_enter()
  File "C:\Users\scott\AppData\Roaming\Python\Python37\site-packages\gs_quant\session.py", line 81, in _on_enter
    self.init()
  File "C:\Users\scott\AppData\Roaming\Python\Python37\site-packages\gs_quant\session.py", line 92, in init
    self._authenticate()
  File "C:\Users\scott\AppData\Roaming\Python\Python37\site-packages\gs_quant\session.py", line 270, in _authenticate
    raise MqAuthenticationError(reply.status_code, reply.text, context=self.auth_url)
gs_quant.errors.MqAuthenticationError: context: https://idfs.gs.com/as/token.oauth2
status: 400, message: {"error_description":"The requested scope(s) must be blank or a subset of the provided scopes.","error":"invalid_scope"}

Describe the solution you'd like
The message should be - "your application account needs the following scopes X,Y,Z to invoke the APIs you used. Request scopes at URL"

Are you willing to contribute
No