Return HTTP 406 instead of HTTP 404 when `Accept` cannot be fulfilled about devpi

[zanieb]

PEP 691 suggests three possible options here, one of which is returning a HTTP 406.

[fschulze]

Did you take a look at how warehouse which also uses Pyramid handles that? Did you encounter this as an actual problem yet, or is it to prevent future problems?

[zanieb]

Thanks for the response.

I encountered this problem while working on a package manager. It cannot distinguish between the missing package case and unsupported content type and shows a bad error message to the user.

I haven't looked at warehouse's implementation — I could investigate it though if you're interested in this behavior.

Edit: Here's the relevant implementation https://github.com/pypi/warehouse/blob/4271f2e9e7d9ec28aa5a5a531d3b004bb5f1375f/warehouse/api/simple.py — it looks like they return text/html for unknown types.

[fschulze]

That looks easy enough. Could you check what they do when you send a mismatching accept header? I'm not sure whether that also falls back to text/html. What behavior from PEP 691 would you prefer and why?