plotly.express import raises ModuleNotFound in environment without pandas.

[CarlAndersson]

Importing plotly.express when pandas is not available raises ModuleNotFoundError: No module named 'pandas', instead of the intended ImportError: Plotly express requires pandas to be installed.
This happens on from ._imshow import imshow.
Perhaps this import should be moved below the code that will output a more helpful message?

[emmanuelle]

Thank you @CarlAndersson ! This should be fixed by #2132.