Cannot locate message "MultiArrayLayout" in python ROS bag API

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Hello all,

I get the following error message when parsing a bag file with rosbag API when there is a message of type Int16MultiArray: "Cannot locate message [MultiArrayLayout]: unknown package [std_msgs] on search path [{}]."

Here is the code to parse the bag:

import roslib; roslib.load_manifest('rosbag'); roslib.load_manifest('std_msgs'); 
from std_msgs.msg import Int32, String, Int16MultiArray 
from std_msgs.msg import MultiArrayLayout, MultiArrayDimension 
for topic, msg, t in bag:   
    #do stuff here

As you can see, I include the type that I need (Int16MultiArray) and also it's subtypes (MultiArrayLayout and MultiArrayDimension), but I still get the error. Below is some stack trace.

Traceback (most recent call last):
  File "PowerTransferSensorPositionAnalysis.py", line 163, in <module>
    main()
  File "PowerTransferSensorPositionAnalysis.py", line 53, in main
    for topic, msg, t in bag:
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/rosbag/bag.py", line 2062, in read_messages
    yield self.seek_and_read_message_data_record((entry.chunk_pos, entry.offset), raw)
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/rosbag/bag.py", line 2198, in seek_and_read_message_data_record
    msg_type = _get_message_type(connection_info)
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/rosbag/bag.py", line 1309, in _get_message_type
    message_type = genpy.dynamic.generate_dynamic(info.datatype, info.msg_def)[info.datatype]
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/genpy/dynamic.py", line 151, in generate_dynamic
    for l in msg_generator(msg_context, spec, search_path):
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/genpy/generator.py", line 725, in msg_generator
    genmsg.msg_loader.load_depends(msg_context, spec, search_path)
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/genmsg/msg_loader.py", line 344, in load_depends
    return load_msg_depends(msg_context, spec, msg_search_path)
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/genmsg/msg_loader.py", line 313, in load_msg_depends
    depspec = load_msg_by_type(msg_context, resolved_type, search_path)
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/genmsg/msg_loader.py", line 119, in load_msg_by_type
    file_path = get_msg_file(package_name, base_type, search_path)
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/genmsg/msg_loader.py", line 78, in get_msg_file
    % (base_type, package, search_path))

Thanks for the help

Edit: I should also note that the same error happens when opening the bag with rxbag.