mixer bivariate visualization

[jcfoo]

Hi,

When I try to generate figures using mixer_figures.py two, after a seemingly successful 'fit2' and 'test2' after already calculated univariate results, the message:

--json argument does not contain brute1 optimization results, skip likelihood plot generation

And the last likelihood plot panel is not generated.
I believe I followed the readme steps exactly, and everything else seems to work-- am I missing something simple? I read in another issue that the brute1 optimization is specified by default, but I'm not really sure what is going on. Thank you in advance for your help!