stevedore not works with logging-0.4.9.6

[xutian]

logging has no attribute 'NullHandler', add below code to make a workaround in python2.6

file: /stevedore/__init__.py

try:
    from logging import NullHandler
except ImportError:
    from logging import Handler

    class NullHandler(Handler):
        def emit(self, record):
            pass

[Doug Hellmann (doug-hellmann)]

Unfortunately, we no longer support Python 2.6.