InvalidROSPkgException when running roswtf: no manifest file in roscpp

edit

I am trying to run roswtf as described at the end of the http://www.ros.org/wiki/ROS/Tutorials/Getting%20started%20with%20roswtf (beginner tutorial), but it complains about roscpp not having a manifest file:

WARNING(s) in /opt/ros/groovy/share/camera_info_manager/package.xml:
- The test dependency on "rostest" is redundant with: build_depend, run_depend
WARNING(s) in /opt/ros/groovy/share/diagnostic_analysis/package.xml:
- The test dependency on "rosbag" is redundant with: build_depend, run_depend
- The test dependency on "rostest" is redundant with: build_depend
- The test dependency on "diagnostic_msgs" is redundant with: build_depend, run_depend
Package: beginner_tutorials
Traceback (most recent call last):
  File "/opt/ros/groovy/bin/roswtf", line 35, in <module>
    roswtf.roswtf_main()
  File "/opt/ros/groovy/lib/python2.7/dist-packages/roswtf/__init__.py", line 87, in roswtf_main
    _roswtf_main()
  File "/opt/ros/groovy/lib/python2.7/dist-packages/roswtf/__init__.py", line 174, in _roswtf_main
    roswtf.packages.wtf_check(ctx)
  File "/opt/ros/groovy/lib/python2.7/dist-packages/roswtf/packages.py", line 187, in wtf_check
    warning_rule(r, r[0](ctx), ctx)
  File "/opt/ros/groovy/lib/python2.7/dist-packages/roswtf/packages.py", line 68, in manifest_msg_srv_export
    msgs = set(_manifest_msg_srv_export(ctx, 'msg'))
  File "/opt/ros/groovy/lib/python2.7/dist-packages/roswtf/packages.py", line 59, in _manifest_msg_srv_export
    m_file = roslib.manifest.manifest_file(pkg, True)
  File "/opt/ros/groovy/lib/python2.7/dist-packages/roslib/manifest.py", line 118, in manifest_file
    return _manifest_file_by_dir(d, required=required, env=env)
  File "/opt/ros/groovy/lib/python2.7/dist-packages/roslib/manifest.py", line 94, in _manifest_file_by_dir
    """%locals())
roslib.packages.InvalidROSPkgException: 
Package '/opt/ros/groovy/share/roscpp' is improperly configured: no manifest file is present.

What could be the cause of this?

My configuration: Ubuntu 12.10 32b, ROS Groovy