Warning/Exception when querying dtype with use_inf_as_null

[wcbeard]

I see Exception TypeError: 'data type not understood' in 'util._checknull_old' ignored in the ipython notebook warning color after turning on use_inf_as_null.

The code to reproduce it is

import pandas as pd
pd.options.mode.use_inf_as_null = True
pd.DataFrame([[1]]).dtypes

[jreback]

hmm, must be some older code there.....