activator eclipse で [error] Not a valid command: eclipse (similar: help, alias) の時の対処法

playコンソールでeclipseしようとするとエラーでた

[scalaTest] $ eclipse
[error] Not a valid command: eclipse (similar: help, alias)
[error] Not a valid project ID: eclipse
[error] Expected ':' (if selecting a configuration)
[error] Not a valid key: eclipse (similar: deliver, licenses, clean)
[error] eclipse
[error]        ^

対処

project/plugins.sbtの最終行にaddSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "2.5.0")を追記

vim project/plugins.sbt
##略##
addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "2.5.0")

これで解決。