```
sudo apt-get install zstd/xenial-proposed
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Release 'xenial-proposed' for 'zstd' was not found
```
and indeed, a further call to `apt list --upgradable`
does not show `zstd/xenial-proposed` in the list of packages.
I tried to follow the procedure presented on https:/ /wiki.ubuntu. com/Testing/ EnableProposed,
but got blocked at this stage :
``` proposed
sudo apt-get install zstd/xenial-
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Release 'xenial-proposed' for 'zstd' was not found
```
and indeed, a further call to `apt list --upgradable` proposed` in the list of packages.
does not show `zstd/xenial-