Calling TextIOWrapper.tell() while reading the attached gb2312-encoded file like this:

with open('udhr-gb2312.txt', encoding='GB2312') as f: 
    while True: 
       line = f.readline() 
       t = f.tell()
       if not line: 
           break 

gives this result:

Traceback (most recent call last):
  File "test.py", line 4, in <module>
    t = f.tell()
UnicodeDecodeError: 'gb2312' codec can't decode byte 0xb5 in position 0: illegal multibyte sequence

The file seems to be well-formed and can be read without any problem.  It's only the call to tell() that raises an issue.