@wkentaro Thanks for looking at this:
This is only a warning not an error. You’ll see it in the amd64 builds as well. http://build.ros.org/job/Ibin_uT64__jsk_2015_05_baxter_apc__ubuntu_trusty_amd64__binary/266/consoleFull The reason for the job failing is due to it timing out at 120 minutes. It just happens that these warnings are the last thing printed before the job terminates. There’s been an underlying slowdown of the infrastructure, with unknown causes so far: apt-get updates appear to be running slower now · Issue #535 · ros-infrastructure/ros_buildfarm · GitHub
There’s some potential optimizations that could help your package that I’ll follow up more on your ticket.