[1.5.0-RC1] @nowarn annotation does not suppress any warnings

[eed3si9n]

problem

[error] /home/travis/build/lightbend/mima/project/MimaSettings.scala:16:27: @nowarn annotation does not suppress any warnings
[error]     mimaPreviousArtifacts := Set(pluginProjectID.value.withRevision(mimaPreviousVersion)
[error]                           ^
[error] /home/travis/build/lightbend/mima/project/MimaSettings.scala:19:33: @nowarn annotation does not suppress any warnings
[error]     mimaReportSignatureProblems := true,
[error]                                 ^
[error] /home/travis/build/lightbend/mima/project/MimaSettings.scala:20:28: @nowarn annotation does not suppress any warnings
[error]     mimaBinaryIssueFilters ++= Seq(
[error]                            ^
[error] three errors found

This looks some kind of consequence of the 2.12.13 upgrade? Note that @nowarn appears nowhere in this repo.

This was caught by the Scala community build.

Originally posted by @SethTisue in lightbend-labs/mima#608 (comment)

[eed3si9n]

This is a consequence of me adding blanket @scala.annotation.nowarn("cat=other-pure-statement") to build.sbt DSL expressions.

I think we need to add no-warn-nowarn suppression thing somewhere.