Rotate turtlebot 10 degrees about its axis

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Hi all. How are you? How can I turn turtlebot2 10 degrees about its axis and then pause. Note: The robot will not move, it will just rotate 10 degrees once every say 20 seconds. I tried setting the Twist() object's angular velocity in the Z direction but only one wheel moves and ultimately the robot is displaced.

below is my code:

            angular_velocity = radians(10) #10 degs / s

            r = rospy.Rate(5) #5Hz
            #rospy.loginfo("starting loop")
            while not rospy.is_shutdown():
                    rospy.loginfo("in loop")
                    new_angle = (angle + new_angle) % 360
                    real_angle = real_angle + angle
                    #real_angle = rea1_angle + 5
                    rospy.loginfo("after addition")
                    new_angle =  real_angle % 360

                    turn_cmd.angular.z = angular_velocity #turns 10 degrees a second
                    #turn at 10 degrees a second for 1 second  
                    for i in range(5):
                            self.cmd_vel.publish(turn_cmd)
                            r.sleep()
                    #r.sleep()

The above is my logic. But not only does the robot move, it also does not turn 10 degrees as I expect. What am i doing wrong? Thank you very much. Am using ROS indigo kobuki and turtlebot2

That being said - on slightly different note - what would be the favorable values for the rospy.Rate() function and the inner for loop to achieve the 10 or even 30 degree rotation at a relative higher angular velocity, say 25 degrees per second. Because it seems the robot does not work well with low velocities such as 10 degs/s. Some it does not move at all when low velocities are given. Eitherway, thanks.