Installed fuerte but roslocate says "Unknown distribution: 'fuerte'"

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I'm new to ROS, and it seems that years of Linux system administration has not prepared me for this.

I'm running a fresh and up-to-date Ubuntu 12.04 LTS and I installed fuerte via apt-get. I learned that I should be using rosbuild instead of catkin, and I just set up a workspace in ~/fuerte_workspace/sandbox. But when I try the "roslocate" command, I am told that "fuerte" isn't an option.

mstock@scan:~$ roslocate info ethzasl_ptam
Using ROS_DISTRO: fuerte
Traceback (most recent call last):
  File "/usr/bin/roslocate", line 231, in <module>
    roslocate_main()
  File "/usr/bin/roslocate", line 216, in roslocate_main
    data, type_, _ = get_manifest(name, options.distro)
  File "/usr/lib/python2.7/dist-packages/rosinstall/locate.py", line 192, in get_manifest
    data = get_manifest_from_rosdistro(stackage_name, distro_name)
  File "/usr/lib/python2.7/dist-packages/rosinstall/locate.py", line 217, in get_manifest_from_rosdistro
    distribution_cache = get_cached_distribution(index, distro_name)
  File "/usr/lib/python2.7/dist-packages/rosdistro/__init__.py", line 146, in get_cached_distribution
    cache = get_distribution_cache(index, dist_name)
  File "/usr/lib/python2.7/dist-packages/rosdistro/__init__.py", line 162, in get_distribution_cache
    raise RuntimeError("Unknown distribution: '{0}'. Valid distribution names are: {1}".format(dist_name, ', '.join(["'%s'" % d for d in index.distributions.keys()])))
RuntimeError: Unknown distribution: 'fuerte'. Valid distribution names are: 'groovy', 'jade', 'indigo', 'hydro'

My environment contains:

mstock@scan:~$ env | grep ROS
ROS_ROOT=/opt/ros/fuerte/share/ros
ROSLISP_PACKAGE_DIRECTORY=/opt/ros/fuerte/share/common-lisp/ros
ROS_PACKAGE_PATH=/home/mstock/fuerte_workspace/sandbox:/opt/ros/fuerte/stacks:/opt/ros/fuerte/share:/opt/ros/fuerte/share/ros
ROS_MASTER_URI=http://localhost:11311
ROS_WORKSPACE=/home/mstock/fuerte_workspace
ROS_DISTRO=fuerte
ROS_ETC_DIR=/opt/ros/fuerte/etc/ros

What went wrong?