KeyError: key not found: "file"

[floehopper]

This exception recently occurred in production and I thought we should investigate whether it's occurring due to a bug in the code.

[floehopper]

I've reproduced this locally by editing an existing attachment via the link on the Edit Section page and just clicking "Save attachment" without selecting a file.

There should be some validation in place to protect against this, but given the current state of the codebase, it's unclear what the best way to fix it is without introducing unnecessary complexity.

So I've decided to open a new issue which we will aim to tackle once the code is in an easier to understand state.

Closing.