When trying to access a GPG-Smartcard, connected to the machine via a Smartcard
Reader, the GNOME Keyring Manager acts as a man in the middle, preventing GPG
from successfully accessing the data on the Smartcard.

benjamin@linux-6l3e:~> gpg --card-status
gpg: WARNING: The GNOME keyring manager hijacked the GnuPG agent.
gpg: WARNING: GnuPG will not work properly - please configure that tool to not
interfere with the GnuPG system!
gpg: selecting openpgp failed: Nicht unterst�tztes Zertifikat
gpg: OpenPGP Karte ist nicht vorhanden: Nicht unterst�tztes Zertifikat

A workaround to this issue, is to run the command in a root-shell.