Wait for transfer of data and libraries to nbextensions, and avoid transfer if already done
Wait for transfer of data and libraries to nbextensions, and avoid transfer if already done

mwcraig/vpython-jupyter,BruceSherwood/vpython-jupyter,mwcraig/vpython-jupyter,BruceSherwood/vpython-jupyter,mwcraig/vpython-jupyter,BruceSherwood/vpython-jupyter,mwcraig/vpython-jupyter,BruceSherwood/vpython-jupyter