Robot Stay Inside Circular Ring

[webmanoffesto]

I have a Lego Mindstorms brick running ev3dev (open source Linux) and I am writing a Python program for it. I want to enter it in a friendly Sumo style robot competition. Two robots are put inside a circular ring and whoever pushes their opponent outside the ring wins. So I need an "avoid the line" or "stay inside the black line circle" program.

Here is an example video wwwDOTyoutubeDOTcom/watch?v=3tguWcKTXQI&t=110s
I still have to clarify exactly what the ring will be, black area outlined by white, or something different. But I think I can assume I'll be avoiding a bold black line, and I can change that later if I need to.

I'm running ev3dev, brickman v.0.8.0, kernel 4.4.24-16-ev3dev-ev3 on a Lego Mindstorms EV3 programmable brick, revision 0006
I'm using PyCharm IDE and I push the code to the brick over WiFi.

Error:
<ev3dev.core.LargeMotor object at 0xb6903e30>> ignored
robot@ev3dev:~/myproject$ python col-reflect-driveaway-v.2016.12.05.n01.py
0
Traceback (most recent call last):
  File "col-reflect-driveaway-v.2016.12.05.n01.py", line 38, in <module>
    m2.reset()
  File "/usr/lib/python2.7/dist-packages/ev3dev/core.py", line 738, in reset
    self.command = 'reset'
  File "/usr/lib/python2.7/dist-packages/ev3dev/core.py", line 295, in command
    self.set_attr_string('command', value)
  File "/usr/lib/python2.7/dist-packages/ev3dev/core.py", line 216, in set_attr_string
    self._set_attribute(attribute, "{0}".format(value))
  File "/usr/lib/python2.7/dist-packages/ev3dev/core.py", line 204, in _set_attribute
    self._attribute_cache.write(abspath(self._path + '/' + attribute), value)
AttributeError: 'LargeMotor' object has no attribute '_path'
Exception AttributeError: "'LargeMotor' object has no attribute '_path'" in <bound method LargeMotor.__del__ of <ev3dev.core.LargeMotor object at 0xb6960e30>> ignored
robot@ev3dev:~/myproject$ 

Program

#!/usr/bin/env python3
# so that script can be run from Brickman

# I amd combining a "bump into wall, back up, turn 45 degrees, drive forward" program
# and a color sensor col-reflect program
# This is for a "sumo", robot inside of a circle outlined in black, drive forward, if sense black line then turn

# This code (or an earlier version of it) is posted at codepasteDOTnet/zrs5gq

from ev3dev.ev3 import *
from time import sleep


### col-reflect
# Connect EV3 color sensor and check connected.

cl = ColorSensor()
assert cl.connected, "Connect a color sensor to any sensor port"

# Put the color sensor into COL-REFLECT mode
# to measure reflected light intensity.
# In this mode the sensor will return a value between 0 and 100
cl.mode = 'COL-REFLECT'

while True:
   print(cl.value())
   sleep(0.5)

   # I get max 80 with white paper, 3mm separation
   # and 5 with black plastic, same separation

   direction = 1 # Switches between 1 and -1

   m = LargeMotor('outB')
   m.reset()
   m.run_forever(speed_sp=675 * direction)

   m2 = LargeMotor('outA')
   m2.reset()
   m2.run_forever(speed_sp=675)

   print(cl.value())
   sleep(0.5)

   new_color = cl.value()
   print new_color
   if new_color < 10:
     direction *= -1  # Reverse the direction. Forward becomes backward, backward becomes forward
     m.run_timed(time_sp=1000, speed_sp=300 * direction)
     sleep(1)
     print "I am sleeping"
     direction *= -1  # Reverse the direction. Forward becomes backward, backward becomes forward
     m.run_forever(speed_sp=675 * direction)
   touch = new_touch
#######