For Diamondback, we switched our main debian package source to be
http://packages.ros.org/ros/ubuntu .  We made this shift due to load
issues.  We have been mirroring the old code.ros.org source, but this
mirroring is not in place for the upcoming Electric release.

In order to ensure that you will be able to receive the Electric
update properly, we recommend that you go ahead and migrate your
/etc/apt/sources.list.d/ros-latest.list file to use:

http://packages.ros.org/ros/ubuntu

instead of:

http://code.ros.org/packages/ros/ubuntu

thanks,

 -- your friendly neighborhood ROS repository