[yt-dev] Issue #1317: Cannot set background color after changing color map (yt_analysis/yt)

[Hsi-Yu Schive]

New issue 1317: Cannot set background color after changing color map
https://bitbucket.org/yt_analysis/yt/issues/1317/cannot-set-background-color-after-changing

Hsi-Yu Schive:

The following scripts fails.

```
#!python
import yt
ds = yt.load( "enzo/IsolatedGalaxy/galaxy0030/galaxy0030" )
sz = yt.SlicePlot( ds, 'z', 'density', center='c' )
sz.set_cmap( 'density', 'afmhot' )
sz.set_background_color( 'density' )
sz.save()
```

Error messages:
```
#!python
  File "demo.py", line 5, in <module>
    sz.set_background_color( 'density' )
  File "/projects/ncsa/grav/hyschive/yt/yt.ori/yt/visualization/plot_container.py", line 69, in newfunc
    rv = f(*args, **kwargs)
  File "/projects/ncsa/grav/hyschive/yt/yt.ori/yt/visualization/plot_container.py", line 317, in set_background_color
    cmap = yt_colormaps[cmap]
KeyError: 'afmhot'
```

Note that setting background color explicitly works. For example,
```
#!python
sz.set_background_color( 'density', color='black' )
```