The behavior of readline() has changed on 2.2. This 
should be documented.

Example:

Python 2.1 (#1, Jun 22 2001, 17:13:13)
[GCC 2.95.3 20010315 (release) (conectiva)] on 
linux-i386
Type "copyright", "credits" or "license" for more 
information.
>>> open("/etc").readline()
''

Python 2.2b2+ (#1, Nov 27 2001, 21:39:35)
[GCC 2.95.3 20010315 (release) (conectiva)] on 
linux-ppc
Type "help", "copyright", "credits" or "license" for 
more information.
>>> open("/etc").readline()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
IOError: [Errno 21] Is a directory