Deivorous: There are a number of variables that can prevent you from contacting the default keyserver. The default port for HKP/HKPS is sometimes blocked by strict firewalls. I would suggest attempting to fetch the key via a server the supports one of the more common ports. The default HTTP and HTTPS ports tend to be the most viable options. The following is an example using HKPS and the http over TLS/SSL port 443.
gpg --keyserver hkps://pgp.mit.edu:443 --recv-keys C52048C0C0748FEE227D47A2702353E0F7E48EDB
Here is an example using the standard hypertext transfer protocol port 80.
gpg --keyserver hkps://pgp.mit.edu:80 --recv-keys C52048C0C0748FEE227D47A2702353E0F7E48EDB
You can get more detailed output from gpg using the -vvv and --debug-all options. If neither of those work you can skip the PGP signature check by passing --skippgpcheck to makepkg as noted in the pinned post above.
Pinned Comments
WoefulDerelict commented on 2016-05-23 19:35 (UTC) (edited on 2018-08-18 20:22 (UTC) by WoefulDerelict)
This PKGBUILD verifies the authenticity of the source via PGP signatures which are not part of the Arch Linux keyring. In order to complete the process it is necessary to import the key(s) from the ‘validpgpkeys’ array into the user’s keyring before calling makepkg. There is a helpful article explaining this process by one of Arch Linux's developers located here: http://allanmcrae.com/2015/01/two-pgp-keyrings-for-package-management-in-arch-linux/
Instructions on importing keys from a keyserver and how to automate the retrieval process can be found in the Arch Linux wiki here: https://wiki.archlinux.org/index.php/GnuPG#Use_a_keyserver This article also contains helpful information describing the installation of GnuPG, its configuration and usage.
Execute the following to import keys using gpg:
gpg --recv-keys <KEYID - See 'validpgpkeys' array in PKGBUILD>
The PGP signature check can be skipped by passing --skippgpcheck to makepkg.
Consult the makepkg manual page for a full list of options. [https://www.archlinux.org/pacman/makepkg.8.html]