I got the same issue while using docker toolbox. Using one more “https://stackoverflow.com/” before your source path as well as before your target path will resolve this problem. In your case it will look like this:
docker run -ti -h python -v /${pwd}://root/docker -p 9999:9999 ubuntu:latest /bin/bash
if this doesn’t work then try using absolute path with extra “https://stackoverflow.com/” like this:
docker run -ti -h python -v //c/path_to_application://root/docker -p 9999:9999 ubuntu:latest /bin/bash