Simple SRV error in roscopter: 'module' object has no attribute 'srv' [closed]

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I am running fuerte on the Raspberry Pi to connect to an arducopter flight controller using the roscopter package. I followed the roscopter wiki and everything went well in the package installation but when I try to run the roscopter using the following command

  rosrun roscopter roscopter.py --device=/dev/ttyUSB0 --baudrate=115200

I get the following error:

Traceback (most recent call last):
   File "/home/pi/fuerte_workspace/sandbox/roscopter/nodes/roscopter.py", line 373, in <module>
   rospy.Service("/apm/command", roscopter.srv.APMCommand, command_callback)
AttributeError: 'module' object has no attribute 'srv'

Where could the origin of this problem be? Is python not recognizing my python packages?