use specific scipy version

.travis.yml

@@ -59,6 +59,7 @@ install:
   - conda install pytorch=${TORCH_VERSION} ${TOOLKIT} -c pytorch --yes
   - source script/torch.sh
   - pip install flake8 codecov
+  - pip install scipy==1.4.1
   - pip install .[test]
 script:
   - flake8 .