Fix python 3 incompatibility in _get_import_type
Fix python 3 incompatibility in _get_import_type

In python 3 imp.find_module returns None for path of builtin modules,
like sys or builtin. This modules should be handled as stdlib.

Change-Id: I821c9b4b490c031a8d38d75a124b7c25c2f29d08

openstack-dev/hacking,openstack-dev/hacking,hyakuhei/cleantox,zancas/hacking,hyakuhei/cleantox,zancas/hacking