model_averaging.ipynb fails on 3.3rc1

[ColCarroll]

the cell

traces = [trace_0, trace_1, trace_2]
pm.forestplot(traces);              

fails with

AttributeError                            Traceback (most recent call last)
<ipython-input-6-c37537cb6614> in <module>()
      1 traces = [trace_0, trace_1, trace_2]
----> 2 pm.forestplot(traces);

~/anaconda3/envs/pydata_nyc20173.6/lib/python3.6/site-packages/pymc3/plots/forestplot.py in forestplot(trace_obj, varnames, transform, alpha, quartiles, rhat, main, xtitle, xlim, ylabels, chain_spacing, vline, gs, plot_transformed, plot_kwargs)
    197     interval_plot = None
    198
--> 199     nchains = trace_obj.nchains
    200
    201     if varnames is None:

AttributeError: 'list' object has no attribute 'nchains'

[junpenglao]

That's weird, forestplot.py was updated in #2736 but the code being called is not the up-to-date one.

[ColCarroll]

shoot -- that stack trace says it is using the wrong conda env. I will double check!