FIX str.decode in python2.6 does not take keyword arguments
MNT : retain 'replace' and 2.6 compat

Per https://docs.python.org/2/library/stdtypes.html#str.decode
the error handling arg was added in 2.2, but support for kwarg was
only added in 2.7
BUG : fix 2.6 compatbility

fix usage of decode errors arg for 2.6