def _ensure_no_filesystem(device, block_device_manager):
    if block_device_manager.has_filesystem(device):
        raise FilesystemExists(device)
See ``IBlockDeviceAPI.attach_volume``.
dataset/ETHPy150Open ClusterHQ/flocker/flocker/node/agents/blockdevice.py/_ensure_no_filesystem--crossover with--dataset/ETHPy150Open ClusterHQ/flocker/flocker/node/agents/blockdevice.py/IBlockDeviceAsyncAPI.attach_volume