Redirect problem with static file viewing

[rabernat]

I am trying to make a RISE slideshow using pangeo binder which includes a custom CSS file. RISE is configured to look for a css file called rise.css using a relative path. So if my notebook is running at

https://hub.binder.pangeo.io/user/rabernat-pangeo-osn-demo-yxmimdxv/notebooks/Untitled.ipynb

it looks for

https://hub.binder.pangeo.io/user/rabernat-pangeo-osn-demo-yxmimdxv/notebooks/rise.css

Trying to access that url leads to a redirect to

https://hub.binder.pangeo.io/hub/edit/rise.css

which gives a 404 of course. But I know the file is accessible via

https://hub.binder.pangeo.io/user/rabernat-pangeo-osn-demo-yxmimdxv/files/rise.css

Instead, if I try this on regular binder,

https://hub.gke2.mybinder.org/user/rabernat-pangeo-osn-demo-vhgihnr9/notebooks/rise.css

redirects correctly to

https://hub.gke2.mybinder.org/user/rabernat-pangeo-osn-demo-vhgihnr9/files/rise.css

This suggests a configuration problem in pangeo binder.