pydata/pandas — pull request #6054 by shoyer (2014-01-23 21:41:08+00:00)
Title: DOC: Clarify that DataFrame string formatters must return strings

I am not 100% sure that string formatters must really return *unicode* strings
(non-unicode strings seem to work, too), but I am leaving that because it's
what is already documented.

Fixes #6052.