when removing mod_ruby-1.0.2-alt, we have:

httpd: could not open document config file /etc/httpd/conf/addon-modules/mod_ruby.conf
[FAILED]
error: execution of %postun scriptlet from mod_ruby-1.0.2-alt2 failed, exit status 1

this is because at that stage mod_ruby.conf is already mod_ruby.conf.rpmsave if it was modified.
---

---
trickster:~> sudo rpm -e mod_ruby
warning: /etc/httpd/conf/addon-modules/mod_ruby.conf saved as /etc/httpd/conf/addon-modules/mod_ruby.conf.rpmsave
Shutting down httpd: [  OK  ]
Checking configuration sanity for httpd:  [Wed Jan 15 20:46:22 2003] [warn] module mod_php4.c is already added, skipping
fopen: No such file or directory
httpd: could not open document config file /etc/httpd/conf/addon-modules/mod_ruby.conf
[FAILED]
error: execution of %postun scriptlet from mod_ruby-1.0.2-alt2 failed, exit status 1
trickster:~> l /etc/httpd/conf/addon-modules/mod_ruby.conf
/bin/ls: /etc/httpd/conf/addon-modules/mod_ruby.conf: No such file or directory
trickster:~> l /etc/httpd/conf/addon-modules/             
total 5
-rw-r--r--    1 root     root          850 Jan 10 22:45 mod_fastcgi.conf
-rw-r--r--    1 root     root          850 Nov 13 14:47 mod_fastcgi.conf.bak
-rw-r--r--    1 root     root          250 Nov 13 06:06 mod_php4.conf
-rw-r--r--    1 root     root         1337 Dec 17 18:06 mod_ruby.conf.rpmsave