Can't seem to move TurtleBot2 using Python in Gazebo

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Hi,

I'm currently trying to move a TurtleBot model in Gazebo just by following the instructions on https://learn.turtlebot.com/2015/02/0...

So far I am able to successfully complete all of the previous tutorials on the site. Additionally, when I follow all of the instructions on the page prior to running the provided Python code, I can move the robot in simulation, both with the 2D Nav Goal in rviz and with a keyboard teleop terminal window. Also, I can run the actual TurtleBot2 with the same code; it is only simulation in Gazebo that does not seem to work.

I'm still very new to this so I am not sure how to approach debugging, but I have noticed that the exact point where the code fails to complete is:

success = self.move_base.wait_for_result(rospy.Duration(60))

Also, when I run the code, I noticed in rviz that the robot's local map doesn't appear visually and no navigation planning occurs (again, if I use 2D Nav Goal then the local map and planning occurs normally without issue). Is there any information I can provide that would be useful in diagnosing what the issue is? I am on Ubuntu 16.04 with ROS Kinetic and Gazebo 7. The full provided tutorial code is shown below:

import rospy
from move_base_msgs.msg import MoveBaseAction, MoveBaseGoal
import actionlib
from actionlib_msgs.msg import *

class GoForwardAvoid():
def __init__(self):
    rospy.init_node('nav_test', anonymous=False)

#what to do if shut down (e.g. ctrl + C or failure)
rospy.on_shutdown(self.shutdown)


#tell the action client that we want to spin a thread by default
self.move_base = actionlib.SimpleActionClient("move_base", MoveBaseAction)
rospy.loginfo("wait for the action server to come up")
#allow up to 5 seconds for the action server to come up
self.move_base.wait_for_server(rospy.Duration(5))

#we'll send a goal to the robot to move 3 meters forward
goal = MoveBaseGoal()
goal.target_pose.header.frame_id = 'base_link'
goal.target_pose.header.stamp = rospy.Time.now()
goal.target_pose.pose.position.x = 3.0 #3 meters
goal.target_pose.pose.orientation.w = 1.0 #go forward

#start moving
    self.move_base.send_goal(goal)

#allow TurtleBot up to 60 seconds to complete task
success = self.move_base.wait_for_result(rospy.Duration(60)) 


if not success:
            self.move_base.cancel_goal()
            rospy.loginfo("The base failed to move forward 3 meters for some reason")
    else:
    # We made it!
    state = self.move_base.get_state()
    if state == GoalStatus.SUCCEEDED:
        rospy.loginfo("Hooray, the base moved 3 meters forward")



def shutdown(self):
    rospy.loginfo("Stop")


if __name__ == '__main__':
try:
    GoForwardAvoid()
except rospy.ROSInterruptException:
    rospy.loginfo("Exception thrown")