This plugin is meant to be used in conjunction with sbt-pgp. sbt-pgp has a
checkPgpSignatures command, that can validate the PGP keys of your dependencies. sbt-pgp-coursier ensures coursier is used during the resolution triggered by
checkPgpSignatures, that downloads PGP signatures in particular.
Add sbt-pgp-coursier to
addSbtPlugin("io.get-coursier" % "sbt-pgp-coursier" % "1.1.0-M13-4")
checkPgpSignatures from sbt-pgp then relies on coursier to download artifacts,
$ sbt checkPgpSignatures