What is movementmotor and how do I fix it?

I picked up this script from a free unity program but it is telling me it does not recognize MovementMotor. how do I fix this and what do I replace it with. here is the script that I have where movementmotor is used. it is from the angry bots tutorial from unity. The error message I get is

 assets/Standard Assets/Scripts/AI scripting/AttackMoveController,js(4,20): BCE0018: The name 'MovementMotor' does not denote a valid type ('not found').

The code I use is:

 #pragma strict
 
 // Public member data
 public var motor : MovementMotor;
 
 public var targetDistanceFront : float = 2.5;
 public var targetDistanceBack : float = 1.0;
 
 public var weaponBehaviour : MonoBehaviour;
 
 // Private memeber data
 private var character : Transform;
 private var nextPatrolPoint : int = 0;
 
 private var player : Transform;
 
 private var goingRight : float = 1;
 private var directionChangeTime : float = 0;
 
 function Awake () {
     character = motor.transform;
     player = GameObject.FindWithTag ("Player").transform;
 }
 
 function OnEnable () {
     if (weaponBehaviour)
         weaponBehaviour.enabled = true;
 }
 
 function OnDisable () {
     if (weaponBehaviour)
         weaponBehaviour.enabled = false;
 }
 
 function Update () {
     // Calculate the direction from the player to this character
     var playerToCharacterDirection : Vector3 = (character.position - player.position);
     //playerToCharacterDirection.y = 0;
     playerToCharacterDirection.Normalize ();
     
     // Set this character to face the player,
     // that is, to face the direction from this character to the player
     motor.facingDirection = -playerToCharacterDirection;
     
     // Calculate the angle in degrees this character is away from the front of the character.
     // If this character is in front of the player, the angle is 0,
     // to the side is 90 and behind is 180.
     var degreesFromPlayerForward : float = Vector3.Angle (playerToCharacterDirection, player.forward);
     
     // If not almost directly in front of the player, base the direction on what
     // is the shortest route to get behind the player: Left or right way around.
     if (degreesFromPlayerForward > 30) {
         goingRight = Mathf.Sign (Vector3.Dot (-playerToCharacterDirection, player.right));
         directionChangeTime = Time.time;
     }
     // If this character has stayed in front of the player for more than a little while,
     // change direction to the other way around. This avoids some cases of the character
     // getting stuck while the player is aiming at him.
     else if (Time.time > directionChangeTime + 0.8) {
         goingRight = -goingRight;
         directionChangeTime = Time.time;
     }
     
     // behindFactor is how much this character is behind the player.
     // 0 degrees is a value of 0 and 90 degrees or more is a value of 1.
     var behindFactor : float = Mathf.InverseLerp (0, 90, degreesFromPlayerForward);
     
     // Lerp the target distance between the front and back target distances based on the behindFactor
     var targetDistance : float = Mathf.Lerp (targetDistanceFront, targetDistanceBack, behindFactor);
     
     // Calculate the targetPosition
     var targetPosition : Vector3 = player.position + playerToCharacterDirection * targetDistance;
     
     // If this character is not already behind the player, strafe sideways to get behind
     if (degreesFromPlayerForward < 120)
         targetPosition += character.right * goingRight;
     
     // Calculate the target vector that this character should move along
     // to reach the target position
     var targetVector : Vector3 = targetPosition - character.position;
     targetVector.y = 0;
     
     // Make sure the target vector doesn't exceed a length if one
     if (targetVector.sqrMagnitude > 1)
         targetVector.Normalize ();
     
     // Smooth the movement direction a bit so this character doesn't change direction abruptly
     motor.movementDirection = targetVector;
 }