Description:
If "USERGROUPS_ENAB" is set to yes in "/etc/login.defs" (which it is by default, on Arch), then "userdel" will delete the user's group if it contains no more members. Therefore, the following "groupdel" command in pre_remove() returns in error.

It's the chicken in the egg problem because "userdel" needs to run first otherwise "groupdel" will return in error.


Additional info:
* package version(s)
extra/bitlbee 1.2.6a-1
* config and/or log files etc.
sudo pacman -Rn bitlbee
checking dependencies...
error: command failed to execute correctly
(1/1) removing bitlbee

Here is an untested bitlbee.install providing other modifications.
(And in this case I guess there isn't an effective difference between pre_remove() and post_remove())

Other Stuff
the bitlbee PKGBUILD should set the "force" option otherwise pacman will not promp for upgrading from 1.2.6 -> 1.2.6a