How to use the locust.exception.LocustError function in locust

def __init__(self):
        super(ProgramsUser, self).__init__()

        if not self.host:
            raise LocustError(
                'You must specify a base host, either in the host attribute in the Locust class, '
                'or on the command line using the --host option.'
            )

        self.client = LocustEdxRestApiClient(
            PROGRAMS_API_URL,
            session=HttpSession(base_url=self.host),
            jwt=self._get_token()
        )

def __init__(self):
        super(FastHttpLocust, self).__init__()
        if self.host is None:
            raise LocustError("You must specify the base host. Either in the host attribute in the Locust class, or on the command line using the --host option.")
        if not re.match(r"^https?://[^/]+$", self.host, re.I):
            raise LocustError("Invalid host (`%s`). The specified host string must be a base URL without a trailing slash. E.g. http://example.org" % self.host)
        
        self.client = FastHttpSession(base_url=self.host)

class LocustError(Exception):
    pass

class ResponseError(Exception):
    pass

class CatchResponseError(Exception):
    pass

class MissingWaitTimeError(LocustError):
    pass

class InterruptTaskSet(Exception):
    """
    Exception that will interrupt a Locust when thrown inside a task
    """
    
    def __init__(self, reschedule=True):
        """
        If *reschedule* is True and the InterruptTaskSet is raised inside a nested TaskSet,
        the parent TaskSet whould immediately reschedule another task.
        """
        self.reschedule = reschedule

class StopLocust(Exception):
    pass

def _send_obj(sock, msg):
    data = msg.serialize()
    packed = struct.pack('!i', len(data)) + data
    try:
        sock.sendall(packed)
    except Exception:
        try:
            sock.close()
        except:
            pass
        finally:
            raise LocustError("Slave has disconnected")

def run(self, runner=None):
        task_set_instance = self.task_set(self)
        try:
            task_set_instance.run()
        except StopLocust:
            pass
        except (RescheduleTask, RescheduleTaskImmediately) as e:
            six.reraise(LocustError, LocustError("A task inside a Locust class' main TaskSet (`%s.task_set` of type `%s`) seems to have called interrupt() or raised an InterruptTaskSet exception. The interrupt() function is used to hand over execution to a parent TaskSet, and should never be called in the main TaskSet which a Locust class' task_set attribute points to." % (type(self).__name__, self.task_set.__name__)), sys.exc_info()[2])
        except GreenletExit as e:
            if runner:
                runner.state = STATE_CLEANUP
            # Run the task_set on_stop method, if it has one
            if hasattr(task_set_instance, "on_stop"):
                task_set_instance.on_stop()
            raise  # Maybe something relies on this except being raised?

def __init__(self):
        super(RealBrowserLocust, self).__init__()
        if self.screen_width is None:
            raise LocustError("You must specify a screen_width "
                              "for the browser")
        if self.screen_height is None:
            raise LocustError("You must specify a screen_height "
                              "for the browser")
        self.proxy_server = os_getenv("LOCUST_BROWSER_PROXY", None)

def __init__(self):
        super(RealBrowserLocust, self).__init__()
        if self.screen_width is None:
            raise LocustError("You must specify a screen_width "
                              "for the browser")
        if self.screen_height is None:
            raise LocustError("You must specify a screen_height "
                              "for the browser")
        self.proxy_server = os_getenv("LOCUST_BROWSER_PROXY", None)

def __init__(self):
        super(HttpLocust, self).__init__()
        if self.host is None:
            raise LocustError("You must specify the base host. Either in the host attribute in the Locust class, or on the command line using the --host option.")

        session = HttpSession(base_url=self.host)
        session.trust_env = self.trust_env
        self.client = session

def __getattr__(self, _):
        raise LocustError("No client instantiated. Did you intend to inherit from HttpLocust?")