sort() is inplace for lists, so it doesn't return the sorted list.
Make sure to strip each line read from the packages* files. In the
installPackages() function, concat the packages list on to the
arglist because that's what yummain is expecting.
We get a file descriptor as returned by os.open() when calling
tempfile.mkstemp(), so we need to pass that value to os.fdopen()
before we can write text to it (easily, anyway).
