_DummyAxis needs a __name__ attribute for ScalarFormatter #17624
Description
Bug report
Bug summary
ScalarFormatter.format_data_short(x) uses self.axis__name__ to get xaxis or yaxis info. If the instance was made with a _DummyAxis instance, however, it fails.
Code for reproduction
See next comment.
Matplotlib version
Master (3.2.1.post2853+g15c0d7c39)