$ rpmquery -p --scripts i586/RPMS/hal-0.5.3-alt4.i586.rpm 
preinstall scriptlet (through /bin/sh):
# Add the "haldaemon" user
/usr/sbin/useradd -c 'HAL daemon' \
        -s /sbin/nologin -r -d '/' haldaemon 2> /dev/null || :
postinstall scriptlet (through /bin/sh):
/usr/sbin/post_service hal
preuninstall scriptlet (through /bin/sh):
/usr/sbin/preun_service hal
postuninstall scriptlet (through /bin/sh):

The %postun scriptlet is not needed at all.
[ -x /etc/rc.d/init.d/hal ] && /etc/rc.d/init.d/hal condrestart
Steps to Reproduce:
rpmi -e hal
Actual Results:  
error: execution of %postun scriptlet from hal-0.5.3-alt4 failed, exit status 1