I'm attempting to compile the ethzasl_ptam stack. The ptam_comm code was compiling fine until recently, I am completely unsure what is wrong.

Running rosmake ptam results in the following error from ptam_comm:

 [  0%] Built target rosbuild_premsgsrvgen
  make[3]: Entering directory `/home/linaro/ros/ethzasl_ptam/ptam_com/build'
  make[3]: Leaving directory `/home/linaro/ros/ethzasl_ptam/ptam_com/build'
  make[3]: Entering directory `/home/linaro/ros/ethzasl_ptam/ptam_com/build'
  [  5%] Generating ../msg_gen/lisp/ptam_info.lisp, ../msg_gen/lisp/_package.lisp, ../msg_gen/lisp/_package_ptam_info.lisp
  Traceback (most recent call last):
    File "/opt/ros/fuerte/share/common-lisp/ros/roslisp/rosbuild/scripts/genmsg_lisp.py", line 871, in <module>
      generate_msg(sys.argv[1])
    File "/opt/ros/fuerte/share/common-lisp/ros/roslisp/rosbuild/scripts/genmsg_lisp.py", line 743, in generate_msg
      write_md5sum(s, spec)
    File "/opt/ros/fuerte/share/common-lisp/ros/roslisp/rosbuild/scripts/genmsg_lisp.py", line 596, in write_md5sum
      compute_files=False)
    File "/opt/ros/fuerte/lib/python2.7/dist-packages/roslib-1.8.10-py2.7.egg/roslib/gentools.py", line 311, in get_dependencies
      _add_msgs_depends(rospack, spec, deps, package)
    File "/opt/ros/fuerte/lib/python2.7/dist-packages/roslib-1.8.10-py2.7.egg/roslib/gentools.py", line 109, in _add_msgs_depends
      _add_msgs_depends(rospack, depspec, deps, package_context)
    File "/opt/ros/fuerte/lib/python2.7/dist-packages/roslib-1.8.10-py2.7.egg/roslib/gentools.py", line 75, in _add_msgs_depends
      valid_packages = valid_packages + rospack.get_depends(package_context, implicit=True)
  TypeError: can only concatenate list (not "set") to list
  make[3]: *** [../msg_gen/lisp/ptam_info.lisp] Error 1
  make[3]: Leaving directory `/home/linaro/ros/ethzasl_ptam/ptam_com/build'
  make[2]: *** [CMakeFiles/ROSBUILD_genmsg_lisp.dir/all] Error 2
  make[2]: Leaving directory `/home/linaro/ros/ethzasl_ptam/ptam_com/build'
  make[1]: *** [all] Error 2
  make[1]: Leaving directory `/home/linaro/ros/ethzasl_ptam/ptam_com/build'
-------------------------------------------------------------------------------}
[ rosmake ] Output from build of package ptam_com written to:
[ rosmake ]    /home/linaro/.ros/rosmake/rosmake_output-20130625-150340/ptam_com/build_output.log
[rosmake-1] Finished <<< ptam_com [FAIL] [ 12.06 seconds ]                                                                                                
[ rosmake ] Halting due to failure in package ptam_com. 
[ rosmake ] Waiting for other threads to complete.                                               
[ rosmake ] Output from build of package bullet written to:                                                                     [ 1 Active 8/26 Complete ]
[ rosmake ]    /home/linaro/.ros/rosmake/rosmake_output-20130625-150340/bullet/build_output.log
[rosmake-0] Finished <<< bullet [PASS] [ 33.47 seconds ] -- WARNING: 4 compiler warnings                                                                  
[ rosmake ] Results:                                                                                                                                      
[ rosmake ] Built 10 packages with 1 failures.                                                                                                            
[ rosmake ] Summary output to directory                                                                                                                   
[ rosmake ] /home/linaro/.ros/rosmake/rosmake_output-20130625-150340     

The error message indicates a problem with one of the core ros python files, however, even after re-building ROS from source, I am still getting the error. What's wrong?