Print hints when pulling images triggered “toomanyrequests”

[reliveyy]

Pulling exchangeunion/xud:1.2.1...
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/docker/api/client.py", line 259, in _raise_for_status
    response.raise_for_status()
  File "/usr/local/lib/python3.8/site-packages/requests/models.py", line 943, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 500 Server Error: Internal Server Error for url: http+docker://localhost/v1.40/images/create?tag=1.2.1&fromImage=exchangeunion%2Fxud

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/launcher-1.0.0-py3.8.egg/launcher/__init__.py", line 276, in launch
    env.start()
  File "/usr/local/lib/python3.8/site-packages/launcher-1.0.0-py3.8.egg/launcher/__init__.py", line 245, in start
    up_env = self.node_manager.update()
  File "/usr/local/lib/python3.8/site-packages/launcher-1.0.0-py3.8.egg/launcher/node/__init__.py", line 299, in update
    self.image_manager.update_images()
  File "/usr/local/lib/python3.8/site-packages/launcher-1.0.0-py3.8.egg/launcher/node/image.py", line 365, in update_images
    output = self.client.api.pull(repo, tag=tag, stream=True, decode=True)
  File "/usr/local/lib/python3.8/site-packages/docker/api/image.py", line 415, in pull
    self._raise_for_status(response)
  File "/usr/local/lib/python3.8/site-packages/docker/api/client.py", line 261, in _raise_for_status
    raise create_api_error_from_http_exception(e)
  File "/usr/local/lib/python3.8/site-packages/docker/errors.py", line 31, in create_api_error_from_http_exception
    raise cls(e, response=response, explanation=explanation)
docker.errors.APIError: 500 Server Error: Internal Server Error ("toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit")