Remove some more 'is' in favor of '=='.
Remove some more 'is' in favor of '=='.

GabrielNicolasAvellaneda/riak-python-client,GabrielNicolasAvellaneda/riak-python-client,basho/riak-python-client,basho/riak-python-client,bmess/riak-python-client,basho/riak-python-client,bmess/riak-python-client