showPlanProblem (PackageCycle cycleGroup) =
     "The following packages are involved in a dependency cycle "
  ++ intercalate ", " (map (display.packageId) cycleGroup)
showPlanProblem (PackageCycle cycleGroup) =
     "The following packages are involved in a dependency cycle "
  ++ intercalate ", " (map (display.packageId) cycleGroup)
showPlanProblem (PackageCycle cycleGroup) =
     "The following packages are involved in a dependency cycle "
  ++ intercalate ", " (map (display.packageId) cycleGroup)