message: Clarify error message of plot_model when pydot is not installed.
diff: @@ -104,9 +104,10 @@ def model_to_dot(model,
  if not check_pydot():
  message = (
  - 'Failed to import pydot. You must `pip install pydot` '
  - 'and install graphviz (https://graphviz.gitlab.io/download/), ',
  - 'for `pydotprint` to work.')
  + 'You must install pydot (`pip install pydot`) '
  + 'and install graphviz '
  + '(see instructions at https://graphviz.gitlab.io/download/) ',
  + 'for plot_model/model_to_dot to work.')
  if 'IPython.core.magics.namespace' in sys.modules:
  # We don't raise an exception here in order to avoid crashing notebook
  # tests where graphviz is not available.
  