bash-3.2$ sudo easy_install appscript
Password:
Searching for appscript
Reading http://pypi.python.org/simple/appscript/
Reading http://appscript.sourceforge
I found another solution here which solves the problem once and for all. It turns out XCode4 still has the ppc assembler. You just need a symlink to it in the right place:
$ sudo ln -s /Developer/Platforms/iPhoneOS.platform/Developer/usr/libexec/gcc/darwin/ppc /Developer/usr/libexec/gcc/darwin
$ sudo ln -s /Developer/Platforms/iPhoneOS.platform/Developer/usr/libexec/gcc/darwin/ppc /usr/libexec/gcc/darwin
Fixed the problem for me with XCode4 installed on Snow Leopard.
EDIT: I tried other solutions, which worked in some cases, but invariably encountered a package that hardcoded the PPC requirement somewhere. Providing the PPC assembler got rid of all these problems once and for all.