Build system problems for x86_64 in development

["Jose' Matos" <jamatos fc up pt>]

All my requested build for x86_64 (and only in this arch) in development have 
failled:

Executing /usr/sbin/mock-helper 
yum --installroot /var/lib/mock/fedora-development-x86_64-core-3b41e5a8163cb20c44749cf4f5c5198c0c70dbb3/root 
groupinstall build
file:///pub/fedora/linux/core/development/x86_64/os/repodata/repomd.xml: 
[Errno 5] OSError: [Errno 2] No such file or 
directory: '/pub/fedora/linux/core/development/x86_64/os/repodata/repomd.xml'
Trying other mirror.
Cannot open/read repomd.xml file for repository: core
failure: repodata/repomd.xml from core: [Errno 256] No more mirrors to try.
Cleaning up...

-- 
José Abílio