* Build snaps using core20 (vs core)
* Use ols-goodyear for the dependencies
* Update snapcraft.yaml to work with newer snapcraft versions
* Bumped version to 1.1 (as there is a base update)
Updates
* snapcraft.yaml to use core20 as a base (coming from core!)
* Makefile to use the curated wheels from ols-goodyear
* Makefile to place the virtualenv in a local subdirectory (that was a
problem once, with ancient versions of snapcraft, that prevented this)
* Updated gitignore
* Updated the build & clean commands for a more modern snapcraft
* removed libsodium as it no longer needed
Tarballs produced by `snap-store-proxy fetch-snaps` can contain
channel-maps with more revisions than snap files of those revisions.
Skip missing revisions if they're not included in the tarball while
trying to push snap files to an airgapped proxy.
TODO: This function is not tested and should probably be, but lots of
the code is repeated with the one from snap-store-proxy, so we might
want to fix that by deduplicating it into a library.
