superscripts in bokeh axis labels display as "$^2$ about sherpa

[DougBurke]

I've also seen an issue with an X-axis label (from one of the flux routines), but that's not surprising.

[hamogu]

A limitation of the current version of bokeh is that the $ can only appear in the beginning and the end of a string, not in the middle (https://docs.bokeh.org/en/latest/docs/user_guide/styling/mathtext.html#latex). For most labels, I've edited the labels to use math notation all the way through and then mark the non-math text: $$\mathrm{f(E) Photons/sec/cm}^2\mathrm{/keV}$$

Bokeh plans to generalize that; it might be fixed in the next release with no effort on our side.