'utf-8' codec can't decode byte reading a file in Python3.4 but not in Python2.7

Question

I was trying to read a file in python2.7, and it was readen perfectly. The problem that I have is when I execute the same program in Python3.4 and then appear the error:

Answer 1

Ok, I did the same as @unutbu tell me. The result was a lot of encodings one of these are cp1250, for that reason I change :

f = open(filename,'r')

to

f = open(filename,'r', encoding='cp1250')

like @triplee suggest me. And now I can read my files.