PYTHON-1849 Ignore patch_all return value added in gevent 1.4+
PYTHON-1849 Ignore patch_all return value added in gevent 1.4+

mongodb/mongo-python-driver,ShaneHarvey/mongo-python-driver,ShaneHarvey/mongo-python-driver,mongodb/mongo-python-driver,mongodb/mongo-python-driver,ShaneHarvey/mongo-python-driver