log=True bar plots are raising with mpl 1.2.1

Commited today in #3247 looks like a regression from mpl 1.2.0.

xref:matplotlib/matplotlib#1882

disabled failing test in fc355b1, revert the revert when the mpl issues is resolved.

[tacaswell]

A work around is to specify the bottom kwarg explicitly. There is a PR to fix it as well.

PR: matplotlib/matplotlib#1889

see my comment there, why are you working around a regression instead of reversing
the changed behaviour? that will cause inconsistent behaviour across mpl versions.

[tacaswell]

There is PR to fix the regression, but if you want to patch your code to work right now there is a way to by pass the problematic block in a way that will be valid no matter what.

yes please. what is it?