Flake8 currently ignores the following errors:
H238: old style class declaration, use new style (inherit from object)
H237: module is removed in Python 3
H236: Use six.add_metaclass instead of __metaclass__
Enable them for python3 style code
Story: 2004515
Task: 28571
Change-Id: Ia57e12756c187de4713ce994e3b79f2a5d9f3124
Signed-off-by: Eric Barrett <eric.barrett@windriver.com>