enforce clean notebooks (#210)

.github/workflows/ci.yaml

@@ -33,7 +33,7 @@ jobs:
           echo "Check we are starting with clean git checkout"
           if [ -n "$(git status -uno -s)" ]; then echo "git status is not clean"; false; fi
           echo "Trying to strip out notebooks"
-          nbdev_clean
+          ./action_files/clean_nbs
           echo "Check that strip out was unnecessary"
           git status -s # display the status to see which nbs need cleaning up
           if [ -n "$(git status -uno -s)" ]; then echo -e "!!! Detected unstripped out notebooks\n!!!Remember to run nbdev_install_hooks"; false; fi