Mac OS X Snow Leopard no puede instalar Python 2.7 readline

Cuando intento

pip install readline

o

easy_install readline

Me aparece el siguiente error

Running readline-6.1.0/setup.py -q bdist_egg --dist-dir /var/folders/uX/uXgzCdzXEfSGJugKNxAMx++++TI/-Tmp-/easy_install-XhqAku/readline-6.1.0/egg-dist-tmp-I7rsWF
/usr/libexec/gcc/powerpc-apple-darwin10/4.2.1/as: assembler (/usr/bin/../libexec/gcc/darwin/ppc/as or /usr/bin/../local/libexec/gcc/darwin/ppc/as) for architecture ppc not installed
Installed assemblers are:
/usr/bin/../libexec/gcc/darwin/x86_64/as for architecture x86_64
/usr/bin/../libexec/gcc/darwin/i386/as for architecture i386
lipo: can't open input file: /var/folders/uX/uXgzCdzXEfSGJugKNxAMx++++TI/-Tmp-//cc3nFYj0.out (No such file or directory)
error: Setup script exited with error: command 'gcc-4.2' failed with exit status 1

Aunque para Python 2.6.1 encuentra readline-6.1.0-py2.6-macosx-10.6-universal.egg y funciona bien, fijando readline para ipython para 2.6.1. Sin embargo, no funciona para 2.7.