Built-in file objects allow repeated calls to .close(), even the
documentation states, "Calling close() more than once is allowed."
(http://docs.python.org/lib/bltin-file-objects.html)

GzipFile does not obey this aspect of the file interface:
>>> import gzip
>>> f = gzip.GzipFile('testfile1.gz', 'ab')
>>> f.close()
>>> f.close()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File
"/Library/Frameworks/Python.framework/Versions/2.4//lib/python2.4/gzip.py",
line 315, in close
    self.fileobj.write(self.compress.flush())
AttributeError: 'NoneType' object has no attribute 'write'

The gzip documentation does not document this (mis-)behavior.

(Trivial) patch against 2.4.3 gzip.py attached.