Unable to use mock or rfpkg mockbuild

Hi, I'm trying to rebuild a package (my system is Fedora 31) but I get KeyError: 'yum.conf' ERROR: Error in configuration Could not execute mockbuild: Failed to execute command. with $ rfpkg mockbuild or with $ mock -r fedora-30-i386-rpmfusion_free source.rpm I have mock-rpmfusion-free-32.0-1.fc31.noarch installed Regards, Sergio