test_invalid_colormap: ValueError not raised
```
======================================================================
FAIL: test_invalid_colormap (pandas.tests.test_graphics.TestDataFrameGroupByPlots)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/yoh/deb/gits/pkg-exppsy/build-area/pandas-0.11.0+git43-g7b2eaa4/debian/tmp/usr/lib/python2.7/dist-packages/pandas/tests/test_graphics.py", line 995, in test_invalid_colormap
    self.assertRaises(ValueError, df.plot, colormap='invalid_colormap')
AssertionError: ValueError not raised
```

that is under Agg backend and matplotlib 1.1.1~rc2-1
