This line returns nothing:
yum --enablerepo=sl-source list available *src.rpm
Loaded plugins: aliases, changelog, downloadonly, fastestmirror, refresh-
               : packagekit, security, tmprepo, verify, versionlock
Loading mirror speeds from cached hostfile
  * elrepo: elrepo.org
  * epel: mirrors.solfo.com
  * rpmforge: mirror.cpsc.ucalgary.ca
  * sl: ftp1.scientificlinux.org
  * sl-security: ftp1.scientificlinux.org
  * sl-source: ftp1.scientificlinux.org
Error: No matching Packages to list

Now, I know that's not really empty. I just used ftp to download the
libusb1 source RPM. Even getting specific does not work.

yum --enablerepo=sl-source list available libusb1-1.0.3-1.el6.src.rpm
Loaded plugins: aliases, changelog, downloadonly, fastestmirror, refresh-
               : packagekit, security, tmprepo, verify, versionlock
Loading mirror speeds from cached hostfile
  * elrepo: elrepo.org
  * epel: mirrors.solfo.com
  * rpmforge: mirror.cpsc.ucalgary.ca
  * sl: ftp1.scientificlinux.org
  * sl-security: ftp1.scientificlinux.org
  * sl-source: ftp1.scientificlinux.org
Error: No matching Packages to list


Am I suffering a senior moment and missing something important?

{o.o}