Upload icon returns KeyError: u'icon'

[Toto Bille]

API returns KeyError: u'icon' when uploading an non valid icon to a snap that already has an icon.
You can find the issue on sentry: https://sentry.ols.canonical.com/canonical/snapcraft-dashboard/issues/6064/

# Step to reproduce

- Have a snap with a existing icon
- Upload an image too big (example: https://www.bhphotovideo.com/images/images500x500/Rosco_102301642124_E_Colour_164_Flame_Red_163075.jpg)
- API returns: `{'error_list': [{'message': "KeyError: u'icon'", 'code': 'internal-server-error'}]}`

# Excpected behaviour

- Have a snap with a existing icon
- Upload an image too big (example: https://www.bhphotovideo.com/images/images500x500/Rosco_102301642124_E_Colour_164_Flame_Red_163075.jpg)
- API returns: `{'error_list': [{'message': 'Image must be exactly 256x256 pixels in size.', 'code': 'invalid-field', 'extra': {'field': 'icon', 'value': 'blue.png', 'size': 256}}]}`

[Daniel Manrique (roadmr)]

Hello,

When you "Upload an image too big", you're hitting this endpoint:

https://dashboard.snapcraft.io/dev/api/snaps/<your_snap_id>/binary-metadata

Could you perhaps somehow obtain the payload you're sending to this endpoint? I don't think I need the full binary parts for the actual icons, so if you want to elide that, that should be fine.

I tried your repro case and got the expected behavior, so something else is at play here.

[Toto Bille (tbmb)]

Here is the payload that I have send when I upload an image (of wrong size) for a snap that has already has an icon set:

{'info': '[{"key": "red (copy 1).png", "type": "icon", "filename": "red (copy 1).png", "hash": "73f1e44b8bdfdf921f4da13cba884043b835b48c88290097cda0c99fae8f580b"}]'}