A traceback that occurs within a list comprehension (and probably all
comprehensions) only shows the stack from the comprehension, not the
entire scope:

Traceback (most recent call last):
  File "Lib/test/test_multibytecodec_support.py", line 35, in
test_chunkcoding
    for f in self.tstring]):
  File "Lib/test/test_multibytecodec_support.py", line 35, in <listcomp>
    for f in self.tstring]):
UnicodeDecodeError: 'utf8' codec can't decode byte 0xa6 in position 0:
unexpected code byte