It appears that this *does* affect 2.7 (though not 3.2, 3.3 or 3.4, fortunately):

    ~/src/cpython/2.7☿ gdb --ex run --args ./python -c 'import bz2; obj = bz2.BZ2File("/dev/null"); obj.__init__("")'
    «... snip banner ...»
    Starting program: /home.u/nadeem/src/cpython/2.7/./python -c import\ bz2\;\ obj\ =\ bz2.BZ2File\(\"/dev/null\"\)\;\ obj.__init__\(\"\"\)
    [Thread debugging using libthread_db enabled]
    Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    IOError: [Errno 2] No such file or directory: ''

    Program received signal SIGSEGV, Segmentation fault.
    0x0000000000431d3e in PyFile_DecUseCount (fobj=0x0) at Objects/fileobject.c:89
    89          fobj->unlocked_count--;