E275: Warning for parenthesized (yield)

[jpmckinney]

For example:

https://github.com/ICRAR/ijson/blob/3100b96e0c5bd52cda971228dcd61a853ad92257/ijson/common.py#L139-L161

@utils.coroutine
def items_basecoro(target, prefix, map_type=None):
    '''
    An couroutine dispatching native Python objects constructed from the events
    under a given prefix.
    '''
    while True:
        current, event, value = (yield)
        if current == prefix:
            if event in ('start_map', 'start_array'):
                object_depth = 1
                builder = ObjectBuilder(map_type=map_type)
                while object_depth:
                    builder.event(event, value)
                    current, event, value = (yield)
                    if event in ('start_map', 'start_array'):
                        object_depth += 1
                    elif event in ('end_map', 'end_array'):
                        object_depth -= 1
                del builder.containers[:]
                target.send(builder.value)
            else:
                target.send(value)

Output:

E275 missing whitespace after keyword