[Python] make .py scripts compatible with python 2 & 3

bindings/python/scripts/__init__.py

bindings/python/scripts/derivative/dcrba.py

bindings/python/scripts/derivative/lambdas.py

bindings/python/scripts/explog.py

bindings/python/scripts/robot_wrapper.py

bindings/python/scripts/romeo_wrapper.py

bindings/python/scripts/rpy.py

bindings/python/scripts/utils.py

lab/python/exp_integration.py

lab/python/kineinv.py

python/explog.py

python/rpy.py

python/tests.py