$ python -c 'open("/dev/zero").read()'
Traceback (most recent call last):
  File "<string>", line 1, in ?
SystemError: ../Objects/stringobject.c:3316: bad
argument to internal function

Compare with this two variants:

$ python -c 'open("/dev/zero").read(2**31-1)'
Traceback (most recent call last):
  File "<string>", line 1, in ?
MemoryError

$ python -c 'open("/dev/zero").read(2**31)'
Traceback (most recent call last):
  File "<string>", line 1, in ?
OverflowError: long int too large to convert to int

The unsized read should produce either MemoryError or
OverflowError instead of SystemError.

Tested with Python 2.2, 2.3, and 2.4.