ROS not finding installed dependency, 'python-serial'

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I'm attempting to install the 'dynamixel_controllers' package. I have pulled own via the svn and am attempting to 'rosmake'. I receive this error

 Results:                                                            
[ rosmake ] Built 35 packages with 0 failures.                                  
[ rosmake ] Summary output to directory                                         
[ rosmake ] /home/ngs-whitehp/.ros/rosmake/rosmake_output-20130718-224424       
[ rosmake ] WARNING: Rosdep did not detect the following system dependencies as installed: python-serial Consider using --rosdep-install option or `rosdep install dynamixel_tutorials dynamixel_msgs dynamixel_controllers dynamixel_driver`
ngs-whitehp@NGS-whiteHP:~/ros_workspace/dynamixel$ --rosdep-install
--rosdep-install: command not found
ngs-whitehp@NGS-whiteHP:~/ros_workspace/dynamixel$ sudo apt-get install python-serial
Reading package lists... Done
Building dependency tree       
Reading state information... Done
python-serial is already the newest version.
The following packages were automatically installed and are no longer required:
  nite-dev ps-engine libbluetooth-dev bison evtest gforth
  libgstreamer-plugins-base0.10-dev python-bluez libusb-dev gforth-common
  joystick flex libffcall1 openni-dev libgstreamer0.10-dev
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 344 not upgraded.

Even though 'python-serial' is listed as the newest version, i'm still receiving this warning. This is a 10.04 Ubuntu running Electric (yes, I realize it's an old system but it's necessary that I use this and not upgrade at this moment).

Any suggestions? I will be controlling Dynamixel Servos from this machine and I assume I will need to be able to communicate to them via Serial... so this is a bit troubling.