Error shading for logy

[sgnoohc]

I think the error shades for logy is not working properly.
See my skype message.

[aminnj]

I can't seem to reproduce it. If you run python plottery.py (comment out

plottery/plottery.py

Line 916 in 8ed0f76

"ratio_pull": True,

), you should get a stacked plot of bgs, with data and a signal, and the systematic band in the ratio looks fine.