The nixpkgs-unstable channel's programs.sqlite was used to identify
packages producing exactly one binary, and these automatically added
to their package definitions wherever possible.
Without the change `tests` eval failed as:
$ nix build --no-link -f. devpod.tests
error:
error: value is a string while a set was expected
The failure reason is in `package` parameter. It should be a derivation,
not a package name. While at it fixed the command to extract version.