ERR: raise on mutli-index columns as its not implemented in to_excel

Try to the following code, and you will find column labels mismatched with the data in the Excel file :

cols = pd.MultiIndex.from_tuples([('site',''),('2014','height'),('2014','weight')])
df = pd.DataFrame(np.random.randn(10,3), columns=cols)
df.to_excel('test.xlsx', index=False)

I am using pandas v0.16.0.

[jreback]

this is not implemented for a column multi-index, see #4679
for either reading or writing

So, going to change this issue to one for error reporting to raise until this is implemented.

[hsperr]

I'm starting on this one now