[yt-dev] Issue #731: Simple ProfilePlot script triggers a matplotlib warning (yt_analysis/yt)

[Nathan Goldbaum]

New issue 731: Simple ProfilePlot script triggers a matplotlib warning
https://bitbucket.org/yt_analysis/yt/issue/731/simple-profileplot-script-triggers-a

Nathan Goldbaum:

```
#!python

pf = load("IsolatedGalaxy/galaxy0030/galaxy0030")
plot = ProfilePlot(pf.h.all_data(), 'Density', 'Temperature')
```

/usr/local/lib/python2.7/site-packages/matplotlib/axes.py:4747: UserWarning: No labeled objects found. Use label='...' kwarg on individual plots.
  warnings.warn("No labeled objects found. "

Responsible: ngoldbaum