better handling of gitlab authentification error

[svigerske]

If one has specified a GitLab token, but then there is an authentication error (e.g., because the token expired), then this leads to some uncaught exception:

01-08-2024 09:41:46 - 741 ERROR tornado.application Uncaught exception GET / (127.0.0.1)
HTTPServerRequest(protocol='http', host='rubberband.zib.de:443', method='GET', uri='/', version='HTTP/1.1', remote_ip='127.0.0.1')
Traceback (most recent call last):
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/tornado/web.py", line 1569, in _execute
    result = self.prepare()
  File "/opt/rubberband/package-20170825173100/rubberband/handlers/fe/base.py", line 27, in prepare
    self.current_user = self.get_current_user()
  File "/opt/rubberband/package-20170825173100/rubberband/handlers/fe/base.py", line 84, in get_current_user
    self.access_level = get_user_access_level(email)
  File "/opt/rubberband/package-20170825173100/rubberband/utils/gitlab.py", line 48, in get_user_access_level
    group_users = client.groups.get(group_id).members.list(query=user_mail)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/exceptions.py", line 251, in wrapped_f
    return f(*args, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/mixins.py", line 49, in get
    server_data = self.gitlab.http_get(path, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/__init__.py", line 532, in http_get
    streamed=streamed, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/__init__.py", line 506, in http_request
    response_body=result.content)
gitlab.exceptions.GitlabAuthenticationError: 401: invalid_token
01-08-2024 09:41:46 - 815 ERROR tornado.application Uncaught exception in write_error
Traceback (most recent call last):
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/tornado/web.py", line 1569, in _execute
    result = self.prepare()
  File "/opt/rubberband/package-20170825173100/rubberband/handlers/fe/base.py", line 27, in prepare
    self.current_user = self.get_current_user()
  File "/opt/rubberband/package-20170825173100/rubberband/handlers/fe/base.py", line 84, in get_current_user
    self.access_level = get_user_access_level(email)
  File "/opt/rubberband/package-20170825173100/rubberband/utils/gitlab.py", line 48, in get_user_access_level
    group_users = client.groups.get(group_id).members.list(query=user_mail)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/exceptions.py", line 251, in wrapped_f
    return f(*args, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/mixins.py", line 49, in get
    server_data = self.gitlab.http_get(path, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/__init__.py", line 532, in http_get
    streamed=streamed, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/__init__.py", line 506, in http_request
    response_body=result.content)
gitlab.exceptions.GitlabAuthenticationError: 401: invalid_token

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/tornado/web.py", line 1112, in send_error
    self.write_error(status_code, **kwargs)
  File "/opt/rubberband/package-20170825173100/rubberband/handlers/fe/base.py", line 162, in write_error
    self.render("error.html", status_code=status_code, page_title=reason, msg=log_message)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/tornado/web.py", line 766, in render
    html = self.render_string(template_name, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/tornado/web.py", line 905, in render_string
    namespace = self.get_template_namespace()
  File "/opt/rubberband/package-20170825173100/rubberband/handlers/fe/base.py", line 175, in get_template_namespace
    namespace = super(BaseHandler, self).get_template_namespace()
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/tornado/web.py", line 921, in get_template_namespace
    current_user=self.current_user,
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/tornado/web.py", line 1233, in current_user
    self._current_user = self.get_current_user()
  File "/opt/rubberband/package-20170825173100/rubberband/handlers/fe/base.py", line 84, in get_current_user
    self.access_level = get_user_access_level(email)
  File "/opt/rubberband/package-20170825173100/rubberband/utils/gitlab.py", line 48, in get_user_access_level
    group_users = client.groups.get(group_id).members.list(query=user_mail)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/exceptions.py", line 251, in wrapped_f
    return f(*args, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/mixins.py", line 49, in get
    server_data = self.gitlab.http_get(path, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/__init__.py", line 532, in http_get
    streamed=streamed, **kwargs)
  File "/opt/rubberband/production/venv/lib/python3.6/site-packages/gitlab/__init__.py", line 506, in http_request
    response_body=result.content)
gitlab.exceptions.GitlabAuthenticationError: 401: invalid_token
01-08-2024 09:41:46 - 815 ERROR tornado.access  500 GET / (127.0.0.1) 121.41ms

It would be really nice if the exception were caught and Rubberband would display some useful warning or error message instead of a 500 - internal server error.

[svigerske]

Also get exceptions at similar point if not specifying any GitLab URL. So the GitLab connection does not seem to be as optional as claimed in the README.