Help on my basic turtlbot node

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Hello ROS community, I am new to ROS and python programming but I am trying to write a node to have my turtlebot wander around the room bump into things, backup, turn left and keep going. I want the turtlebot to keep doing this simple task as long as I have not pressed CTRL+C. I am borrowing most of the code from Mark Silliman's goforward.py script and combining that with a bump subscriber code I found on the internet. When I run the script it in the terminal the robot does not move. I have turtlebot_bringup minimal.launch before i run it from the workstation. If someone more experienced could look at my code and point out why my node won't publish commands to the turtlebot that would be great. I am not quite familiar with some python syntax and I am sure i'm getting close.... Here is my code

#!/usr/bin/env python
# A very basic TurtleBot script that allows the TurtleBot to wander indefinitely. Press CTRL + C to stop.  To run:
# On TurtleBot:
# roslaunch turtlebot_bringup minimal.launch
# On work station:
# python goforward_bumpandturn.py

import rospy
from geometry_msgs.msg import Twist
from kobuki_msgs.msg import BumperEvent
from math import radians
class goforward_bumpandturn():
    def __init__(self):
        # initiliaze
        rospy.init_node('goforward_bumpandturn', anonymous=False, log_level=rospy.INFO)

        # tell user how to stop TurtleBot
        rospy.loginfo("To stop TurtleBot CTRL + C")

        # What function to call when you ctrl + c    
        rospy.on_shutdown(self.shutdown)

    # Create a publisher which can "talk" to TurtleBot and tell it to move
        # Tip: You may need to change cmd_vel_mux/input/navi to /cmd_vel if you're not using TurtleBot2

        self.cmd_vel = rospy.Publisher('cmd_vel_mux/input/navi', Twist, queue_size=100)
        # Twist is a datatype for velocity
        r = rospy.Rate(10);
        move_cmd = Twist()
    # let's go forward at 0.2 m/s
        move_cmd.linear.x = 0.2
    # let's turn at 0 radians/s
        move_cmd.angular.z = 0


        rospy.spin()


    #def processBump(self,data):  (do I need this?)

        self.bump_Subscriber=rospy.Subscriber('mobile_base/events/bumper', BumperEvent,self,queue_size=10)

       global bump 

       if (state == BumperEvent.PRESSED): 
            bump = True 

        else: 
            bump = False 

        rospy.loginfo("Bumper Event") 
        rospy.loginfo(data.bumper)





        move_cmd2 = Twist()
        move_cmd2.linear.x = (-0.2)
        move_cmd2.angular.z = 0

        turn_cmd = Twist()
        turn_cmd.linear.x = 0
        turn_cmd.angular.z = radians(45)

        rospy.spin()




    #if bump data is received, process here 
    #data.bumper: LEFT (0), CENTER (1), RIGHT (2) 
    #data.state: RELEASED(0), PRESSED(1) 




 # This is the logic statement that tells the robot to publish wheel comands as long as ctrl C is not pressed
 # as long as you haven't ctrl + c keeping doing...
        while not rospy.is_shutdown():

            if bump==False:
                self.cmd_vel.publish(move_cmd)      

            else:
             #45 deg/s in radians/s
            # publish the velocity
                self.cmd_vel.publish(move_cmd2)
                self.cmd_vel.publish(turn_cmd)
            # wait for 0.1 seconds (10 HZ) an
            #d publish again
        r.spin()

    def shutdown(self):
         # stop turtlebot
        rospy.loginfo("Stop TurtleBot")
         # a default Twist has linear.x of 0 and angular.z ...