SyntaxError: unqualified exec is not allowed in function 'from_meta' it contains a nested function with free variables

[chrissunny94]

I got the below error when i tried to run the launch file

roslaunch ros_arduino_python arduino.launch

Traceback (most recent call last): File "/home/chris/final_ws/src/ros_arduino_bridge/ros_arduino_python/nodes/arduino_node.py", line 23, in <module> from ros_arduino_python.arduino_driver import Arduino File "/home/chris/final_ws/src/ros_arduino_bridge/ros_arduino_python/src/ros_arduino_python/arduino_driver.py", line 29, in <module> from serial.serialutil import SerialException File "/usr/local/lib/python2.7/dist-packages/serial/__init__.py", line 17, in <module> from serial import errors, utilities, properties, meta, hooks, test, model File "/usr/local/lib/python2.7/dist-packages/serial/hooks.py", line 15, in <module> from serial import model File "/usr/local/lib/python2.7/dist-packages/serial/model.py", line 1406 exec('%s\n\n%s' % (imports, class_definition), namespace)