chainer: RuntimeError: CUDA environment is not correctly set up

chainer/cuda.py", line 82, in check_cuda_available
    raise RuntimeError(msg)
RuntimeError: CUDA environment is not correctly set up
(see https://github.com/pfnet/chainer#installation).CuPy is not correctly installed. Please check your environment, uninstall Chainer and reinstall it with `pip install chainer --no-cache-dir -vvvv`.

CUDAとpycudaをインストールしてから、
chainerを再インストールすると直る。

pip uninstall chainer
pip install chainer