Error during error handling when token can not be retrieved

[totycro]

Hi,

I just accidentally used the library without the necessary environment variables and got an error during error handling here:
https://github.com/dcs4cop/xcube-gen/blob/master/xcube_gen/jobapi.py#L71

Maybe this raise str(e) could be changed to a raise Exception(e) or just a raise, or not have a try-except in the first place.

from xcube_gen.jobapi import JobApi
api = JobApi()
api.whoami

---------------------------------------------------------------------------
HTTPError                                 Traceback (most recent call last)
/opt/conda/envs/eurodatacube-0.18.5/lib/python3.8/site-packages/xcube_gen/jobapi.py in _get_token_for_client(self)
     67 
---> 68             token.raise_for_status()
     69             return token.json()

/opt/conda/envs/eurodatacube-0.18.5/lib/python3.8/site-packages/requests/models.py in raise_for_status(self)
    940         if http_error_msg:
--> 941             raise HTTPError(http_error_msg, response=self)
    942 

HTTPError: 401 Client Error: Unauthorized for url: https://edc.eu.auth0.com/oauth/token

During handling of the above exception, another exception occurred:

TypeError                                 Traceback (most recent call last)
<ipython-input-3-8b27a29fec2f> in <module>
      1 from xcube_gen.jobapi import JobApi
----> 2 api = JobApi()
      3 api.whoami

/opt/conda/envs/eurodatacube-0.18.5/lib/python3.8/site-packages/xcube_gen/jobapi.py in __init__(self, user_name)
     41         self._auth_client_secret = os.getenv("XCUBE_GEN_AUTH_CLIENT_SECRET")
     42 
---> 43         self._token = self._get_token_for_client()
     44         # self._user_name = self._get_user_info_from_auth0(self._token['access_token'])
     45         if self._token:

/opt/conda/envs/eurodatacube-0.18.5/lib/python3.8/site-packages/xcube_gen/jobapi.py in _get_token_for_client(self)
     69             return token.json()
     70         except BaseException as e:
---> 71             raise str(e)
     72 
     73     def _get_user_info_from_auth0(self, token: str):

TypeError: exceptions must derive from BaseException