This is working as designed. The error is telling you that the argument to bytes.split() must be a string:

>>> b''.split(',')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: a bytes-like object is required, not 'str'

>>> b''.split(b',')
[b'']

Same for str.split():

>>> ''.split(b',')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: must be str or None, not bytes

>>> ''.split(',')
['']