Error with Launchpad uploading 403 Client Error: Forbidden

[Joseph Rushton Wakeling]

Hello all,

Recently I was able to successfully set up Launchpad builds for my ldc2 snap. 
However, auto-upload to the store failed with a 403 Client Error: Forbidden.

The error messages are no more informative than this, so anyone have any idea 
what's going on?

Note that I haven't specified any particular channels or tracks to release to, 
since I assumed there was a difference between uploading and releasing.

Thanks & best wishes,

     -- Joe