<!-- Thank you for contributing. These HTML comments will not render in the issue, but you can delete them once you've read them if you prefer! --> ### Bug description <!-- Use this section to clearly and concisely describe the bug. --> Appmode won't work because it needs to create hidden files and that isn't working now. See [here](https://github.com/oschuett/appmode/issues/64). #### Expected behaviour <!-- Tell us what you thought would happen. --> Launching from https://github.com/binder-examples/appmode should open a session and when I click on `appmode` button #### Actual behaviour There's an error right now so there is a '400 Bad Request' page when you try to open in appmode. Here is [the issues post about the error at the appmode repo](https://github.com/oschuett/appmode/issues/64). ### How to fix The workaround is described [here](https://github.com/oschuett/appmode/issues/64#issuecomment-1433043935). To [my fork of binder-examples appmode](https://github.com/fomightez/appmode), I added a file named `jupyter_notebook_config.py` with `c.ContentsManager.allow_hidden = True` as the content and it fixed it. My version of `jupyter_notebook_config.py`: [jupyter_notebook_config.py](https://github.com/fomightez/appmode/blob/master/jupyter_notebook_config.py) ### How to show it is fixed Go to my fork of the repo [here](https://github.com/fomightez/appmode) and click on `launch binder`. It will open in appmode as it should. It would also be nice to update the badge while at it.