glitch in package-get-base.el
xemacs-21.0-b57/lisp/package-get-base.el says:
(xemacs-devel
filename "xemacs-devel-1.16-pkg.tar.gz"
but ftp://ftp.xemacs.org/pub/xemacs/beta/xemacs-21.0/packages/binary-packages
has nothing newer than xemacs-devel-1.15-pkg.tar.gz