I can confirm that:

- the patch applies cleanly to the release26-maint branch, with the
  exception of the Misc/NEWS portion::

  $ hg branch
  release26-maint
  $ ./python -E -tt Lib/test/regrtest.py test_file
  test_file
  1 test OK.
  $ patch -p0 < /tmp/issue2091.diff 
  patching file Objects/fileobject.c
  Hunk #1 succeeded at 209 (offset 54 lines).
  Hunk #2 succeeded at 2269 (offset 194 lines).
  patching file Misc/NEWS
  Hunk #1 FAILED at 12.
  1 out of 1 hunk FAILED -- saving rejects to file Misc/NEWS.rej
  patching file Lib/test/test_file.py
  Hunk #1 succeeded at 176 (offset 55 lines).

- the added test fails before rebuilding Objects/fileobject.c::

  $ ./python -E -tt Lib/test/regrtest.py test_file
  test_file
  test test_file failed -- Traceback (most recent call last):
    File "/home/tseaver/projects/hg-repo/py-2.6/Lib/test/test_file.py", line 181, in testModeStrings
      f = open(TESTFN, mode)
  IOError: [Errno 2] No such file or directory: '@test'
  
  1 test failed:
      test_file

- the added test passes after rebuilding Objects/fielobject.c::

  $ make
  gcc -pthread -c -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes  -I. -IInclude -I./Include   -DPy_BUILD_CORE -o Objects/fileobject.o Objects/fileobject.c
  ...
  $ ./python -E -tt Lib/test/regrtest.py test_file
  test_file
  1 test OK.