ok, thanks. If I run bash with no startup files, I get expected output.
With my regular start-up files:
$ declare -f command_not_found_handle
[ ! -S /var/run/dbus/system_bus_socket ] && runcnf=0;
[ ! -x /usr/libexec/packagekitd ] && runcnf=0;
if [ $runcnf -eq 1 ]; then
echo "bash: $1: command not found";
Which I found is defined in /etc/profile.d/PackageKit.sh
Putting double-quotes around $@ seems to fix it. I'll post bug report to appropriate maintainer.