For RHEL 3 (and it also appears RHEL 4 and 5) the libreadline shared lib
has no specified lib requirement that satisfies the tgetent and related
symbols. (These symbols are provided by ncursesw, ncurses, curses,
termcap as noted in the python setup.py.) The configure script does not
add these required libs in for the readline tests, and so the autoconf
tests will fail and it will incorrectly determine that readline is not
present (and so not define HAVE_RL_COMPLETION_MATCHES etc.)

I guess this generally does not prevent the readline module from being
compiled since setup.py does its own search for readline and adds in the
needed curses library. It does prevent proper declaration of the
completion_matches function, however. On 32 bit systems this doesn't
matter but on 64 bit ones it does as the undeclared (but present in
libreadline) completion_matches returns a char **.

The fix checked in with r54874 after the 2.5.1 release (issue 1703270)
to Modules/readline.c fixes the problem for completion_matches
specifically, but the problem of incorrect determination of readline
presence still exists.

Attached is a patch to fix the problem: it adds the necessary additional
library to the temporary LIBS definition in the readline tests, using
the same order of curses libs specified in setup.py. (The patch includes
the  changes for the configure script in addition to configure.in.)