My preferred AUR helper for Arch is pacaur, which has a dependency of cower. During the installation of cower on my Arch box I was getting an error importing the PGP key. This was a bit irritating, because it wouldn't allow me to install cower, thus I couldn't install pacaur.
Luckily, this is quite easily fixed by manually importing the key by running the following command:
$ gpg --recv-keys --keyserver hkp://pgp.mit.edu 1EB2638FF56C0C53
Once I did this I was able to install cower without any issue :)