Fedup from Fedora 19 to 20 fails because of missing GPG keys

Fedup upgrade from Fedora 19 to Fedora 20 fails with the message:

Importing GPG key 0xB5F29883:
 Userid     : "RPM Fusion nonfree repository for Fedora (20) <rpmfusion-buildsys@lists.rpmfusion.org>"
 Fingerprint: a84d cf58 46cb 10b6 5c47 6c35 63c0 de8c b5f2 9883
 Package    : rpmfusion-nonfree-release-19-1.noarch (installed)
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-rpmfusion-nonfree-fedora-20

Downloading failed: Didn't install any keys

You can manually import the key by running:

[root@localhost ~]# rpmkeys --import /etc/pki/rpm-gpg/RPM-GPG-KEY-rpmfusion-nonfree-fedora-19

OR you can force fedup to run without GPG checking functionality (which is NOT recommended):

[root@localhost ~]# fedup --nogpgcheck --network 20