scripts that plot need update for headless systems

[kglotfelty]

With matplotlib 3.6.x, the TkAgg backend is now raising an exception if there is no DISPLAY rather than simply falling back to use the headless Agg backend. The scripts that do plotting should be updated to handle this more gracefully

• [x] color_color
• [x] correct_periscope_drift
• [x] ecf_calc
• [x] deflare
• [x] lightcurves.py ?
• [ ] sherpa_contrib.* ?

[DougBurke]

That's nice of the backend.

[DougBurke]

@nplee - does the lightcurve stuff need to be updated for this? I'm less bothered with the sherpa_contrib stuff as I believe, but have not recently checked, that it's primarily for interactive use (although it can still be used in a headless manner, so preferably it should work).

[nplee]

I not sure if it's a terrible priority, since lc_clean/lc_sigma_clip have a plot argument to avoid any sort of error, but it's a simple enough update (#767)