If we will try to split bytes we will got quite strange error in console. 

Traceback (most recent call last):
  File "C:/Users/ProAdmin/Desktop/bug_in_python.py", line 6, in <module>
    byte_message.split(",")
TypeError: a bytes-like object is required, not 'str'

The problem here is that object should be string and in if I convert it to string the error is going. So that mean that there are error in mistake . Correct variant should be :
Traceback (most recent call last):
  File "C:/Users/ProAdmin/Desktop/bug_in_python.py", line 6, in <module>
    byte_message.split(",")
TypeError:  str is required, not a bytes-like object


message = 'Python is fun'
byte_message = bytes(message, 'utf-8')
print(byte_message)
#byte_message.split(",") causes error
str(byte_message).split(",") # works