def check_credentials(self):
        """Verifies key/secret/host combination by making a balance inquiry"""
        try:
            return bool(self.mturk.get_account_balance())
        except NoCredentialsError:
            raise MTurkServiceException("No AWS credentials set!")
        except ClientError:
            raise MTurkServiceException("Invalid AWS credentials!")
        except Exception as ex:
            raise MTurkServiceException(
                "Error checking credentials: {}".format(str(ex))
            )