There is an overlapping issue from 2010: "curses.ascii.isblank() function is broken. It confuses backspace (BS 0x08) with tab (0x09)" http://bugs.python.org/issue9770 

Your patch fixes it too (it should be closed). Note: the patch does not pass tests from Lib/test/test_curses_ascii.py attached to issue9770 (even if the code: `if char_class_name in ('cntrl', 'punct') test = unittest.expectedFailure(test)` is removed) e.g., iscntrl(-1) should be False but it returns True:

  $ ./python
  >>> import curses.ascii
  >>> curses.ascii.iscntrl(-1) #XXX expected False
  True

If we ignore negative ints then isblank, ispunct, iscntrl provided in the curses_ascii.patch are ok.