When downloading some supernova models, e.g., 'nugent-sn1a' (but not all, e.g., 'hsiao'), read_griddata_ascii() is invoked. This function passes each line of an ASCII file to _stripcomment(). However in Python 3 the line object is interpreted as raw bytes, while in Python 2 it is a string, which is what _stripcomment() expects. As a result, Python 3 throws the TypeError "Type str doesn't support the buffer API".