Enhance error handling (UX-wise) for file upload

[phlg]

Errors occurring during the upload of a file on the My files page could use better (or let's say prettier) error handling. In the example below, I'm using a bucket quota exceeded error, but I assume it's the same for every kind of HTTP errors received from the S3 endpoint.

Currently, when the error occurs, the progress bar just freezes, and that's it. The actual error is logged and visible on the devtools :

But it's not ideal to tell end users to open the devtools to check what happened.

I don't have any specific idea on how to make this better, but maybe an alert of some kind geared at the user could be nice, even if it's only a generic one. Of course it would be even better to cater for specific cases (such as when a quota is exceeded) to give the users an accurate idea of what went wrong. This is especially true if they have any agency (such as when a quota is exceeded), but I don't know what's realistically achievable.