TypeError('str expected, not NoneType') in parallel_search mode in NAGO example.

I'm trying to run nago example https://github.com/huawei-noah/vega/blob/master/examples/nas/nago/nago.yml

It works if I set general.parallel_search to False, but fails with somewhat cryptic errors if run with parallel_search:True

Here is the log: https://gist.github.com/akamaus/555582a70f2dd060bff72bf7deb0bb37

and this is python packages installed (I had to manually downgrade click to 7.1.2 in order to dask-server to run at all):

% pip3 list 
Package                Version
---------------------- ---------------------
absl-py                0.12.0
astor                  0.8.1
click                  7.1.2
cloudpickle            1.6.0
dask                   2021.6.0
decorator              4.4.2
distributed            2.18.0
fsspec                 2021.6.0
gast                   0.2.2
google-pasta           0.2.0
grpcio                 1.38.0
h5py                   2.10.0
HeapDict               1.0.1
importlib-metadata     4.5.0
joblib                 1.0.1
Keras-Applications     1.0.8
Keras-Preprocessing    1.1.2
locket                 0.2.1
Markdown               3.3.4
msgpack                1.0.2
networkx               2.5.1
noah-vega              1.4.0
numpy                  1.18.5
opencv-python-headless 4.3.0.38
opt-einsum             3.3.0
pandas                 0.25.2
pareto                 1.1.1.post3
partd                  1.2.0
Pillow                 8.2.0
pip                    21.1.2
pkg-resources          0.0.0
protobuf               3.17.3
psutil                 5.8.0
py-dag                 3.0.1
py-spy                 0.3.7
python-dateutil        2.8.1
pytz                   2021.1
PyYAML                 5.1.2
pyzmq                  22.1.0
scikit-learn           0.21.3
scipy                  1.5.3
setuptools             57.0.0
six                    1.16.0
sortedcontainers       2.4.0
tblib                  1.7.0
tensorboard            1.15.0
tensorboardX           1.9
tensorflow-estimator   1.15.1
tensorflow-gpu         1.15.5
termcolor              1.1.0
tf-models-official     0.0.3.dev1
tf-slim                1.1.0
thop                   0.0.31.post2005241907
toolz                  0.11.1
torch                  1.3.0
torchvision            0.4.1
tornado                6.1
typing-extensions      3.10.0.0
Werkzeug               2.0.1
wheel                  0.36.2
wrapt                  1.12.1
zict                   2.0.0
zipp                   3.4.1

huawei-noah / vega

TypeError('str expected, not NoneType') in parallel_search mode in NAGO example. #123