api/gh/redis/redis should return 401 unauthorized and not 500 internal server error on bad auth requests

[filipecosta90]

Sample trace:

root@ip-172-31-57-104:~# tail -n 20 -f /var/opt/redis-benchmarks-specification-api.log
  File "/usr/local/lib/python3.6/dist-packages/flask/app.py", line 1499, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
  File "/usr/local/lib/python3.6/dist-packages/flask_httpauth.py", line 161, in decorated
    user = self.authenticate(auth, password)
  File "/usr/local/lib/python3.6/dist-packages/flask_httpauth.py", line 238, in authenticate
    return self.verify_password_callback(username, client_password)
  File "/usr/local/lib/python3.6/dist-packages/redis_benchmarks_specification/__api__/api.py", line 48, in verify_password
    auth_server_conn.ping()
  File "/usr/local/lib/python3.6/dist-packages/redis/client.py", line 1378, in ping
    return self.execute_command('PING')
  File "/usr/local/lib/python3.6/dist-packages/redis/client.py", line 901, in execute_command
    return self.parse_response(conn, command_name, **options)
  File "/usr/local/lib/python3.6/dist-packages/redis/client.py", line 915, in parse_response
    response = connection.read_response()
  File "/usr/local/lib/python3.6/dist-packages/redis/connection.py", line 739, in read_response
    response = self._parser.read_response()
  File "/usr/local/lib/python3.6/dist-packages/redis/connection.py", line 484, in read_response
    raise response
redis.exceptions.AuthenticationError: Authentication required
18.116.150.197 - - [17/Aug/2021 17:14:29] "POST /api/gh/redis/redis/commits HTTP/1.1" 500 -