Comment 20 for bug 1577926

I encountered this bug also, and it originated with a shell script that invoked rrdtool and exported a tar file to /tmp. Once this was done, /tmp was apparently owned by user ganglia (the rrdtool user) rather than root. Chown-ing to root:root didn't fix the issue, however. Chmod-ing /tmp to 1777 *did* fix this issue and apt-key was working normally after that.