This is a very common error mostly found in Kali Linux and other Debian flavors of Linux ... You get this error when you try to update the OS using apt-get update ....
Could not create /tmp/apt.conf xxxxxx
the simple solution is
run terminal as root
and then type these two commands
chown root:root /tmp/
chmod go+rwXt /tmp/
and then finally run
apt-get clean
and then your apt-get update will run like charm