async is a reserved keyword in Python 3.7. It can no longer be used as method
parameter. Change the name so that we are ready for Python 3.7.
See: https://www.python.org/dev/peps/pep-0492/#deprecation-plans
Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>