docs: def validate(self, message, schema_name):
          """Validate a message given a schema.
  
          Args:
              message (dict): Loaded JSON of pulled message from Google
                  PubSub.
              schema_name (str): Name of schema to validate ``message``
                  against. ``schema_name`` will be used to look up
                  schema from :py:attr:`.MessageValidator.schemas` dict
          Raises:
              InvalidMessageError: if message is invalid against the
                  given schema.
              InvalidMessageError: if given schema name can not be found.
          """
          err = None
          try:
              jsonschema.validate(message, self.schemas[schema_name])
  
          except KeyError:
              msg = (f'Schema "{schema_name}" was not found (available: '
                     f'{", ".join(self.schemas.keys())})')
              err = {'msg': msg}
  
          except jsonschema.ValidationError as e:
              msg = (f'Given message was not valid against the schema '
                     f'"{schema_name}": {e.message}')
              err = {'msg': msg}
  
          if err:
              logging.error(**err)
              raise exceptions.InvalidMessageError(err['msg'])