ImportError: cannot import name '_validate_lengths'
I updated my skimage package.
pip install --upgrade scikit-imageAnd the problem was solved. It's a problem of version of Skimage, which is solved in 0.14.2. PLus, this version is quite stable.
Installing collected packages: dask, scikit-image Found existing installation: dask 0.19.1 Uninstalling dask-0.19.1: Successfully uninstalled dask-0.19.1 Found existing installation: scikit-image 0.13.0 Uninstalling scikit-image-0.13.0: Successfully uninstalled scikit-image-0.13.0Successfully installed dask-1.0.0 scikit-image-0.14.2
scikit-image 0.14.2 worked with numpy 1.16.3. I installed numpy first and then installed scikit image