Summary

All the old image tests use the classic style, whereas new test we ask contributors to add style='mpl20' to the image_comparison decorator.

@image_comparison('new_style.png', remove_text=True, style='mpl20')

As a first step to making the new style the testing default, we should go through and change all the old image comparison tests to explicitly use the classic style:

@image_comparison('old_style.png', style='classic')

This will hit a lot of the tests, but could be done piecemeal or all in one swoop if someone is clever with writing a parser to add the style kwarg.

Eventually the way to test that everything has been caught will be to change the default to 'mpl20' and make sure none of the image tests fail.