catkin_pkg is missing topological_order

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• Ubuntu 12.04
• ROS Groovy

After installing python-catkin-pkg and ros-groovy-catkin from the ROS debian repositories, and manually creating a catkin workspace and then calling cmake ../src from the build directory, I saw the following error:

/opt/ros/groovy/share/catkin/cmake/em/order_packages.cmake.em:6: error: <type 'exceptions.ImportError'>: No module named topological_order
Traceback (most recent call last):
  File "/usr/bin/empy", line 3288, in <module>
    if __name__ == '__main__': main()
  File "/usr/bin/empy", line 3286, in main
    invoke(sys.argv[1:])
  File "/usr/bin/empy", line 3269, in invoke
    interpreter.wrap(interpreter.file, (file, name))
  File "/usr/bin/empy", line 2273, in wrap
    self.fail(e)
  File "/usr/bin/empy", line 2264, in wrap
    apply(callable, args)
  File "/usr/bin/empy", line 2337, in file
    self.safe(scanner, done, locals)
  File "/usr/bin/empy", line 2379, in safe
    self.parse(scanner, locals)
  File "/usr/bin/empy", line 2399, in parse
    token.run(self, locals)
  File "/usr/bin/empy", line 1410, in run
    interpreter.execute(self.code, locals)
  File "/usr/bin/empy", line 2576, in execute
    exec statements in self.globals
  File "<string>", line 3, in <module>
ImportError: No module named topological_order
CMake Error at /opt/ros/groovy/share/catkin/cmake/safe_execute_process.cmake:11 (message):

  execute_process(/home/jbohren/versioned/ros/maintain_catkin/ws/build/catkin_generated/env_cached.sh
  /usr/bin/empy --raw-errors -F
  /home/jbohren/versioned/ros/maintain_catkin/ws/build/catkin_generated/order_packages.py
  -o
  /home/jbohren/versioned/ros/maintain_catkin/ws/build/catkin_generated/order_packages.cmake
  /opt/ros/groovy/share/catkin/cmake/em/order_packages.cmake.em) returned
  error code 1
Call Stack (most recent call first):
  /opt/ros/groovy/share/catkin/cmake/em_expand.cmake:17 (safe_execute_process)
  /opt/ros/groovy/share/catkin/cmake/catkin_workspace.cmake:34 (em_expand)
  CMakeLists.txt:45 (catkin_workspace)


-- Configuring incomplete, errors occurred!