use LeonFatalError to exit

src/main/scala/leon/LeonFatalError.scala

+package leon
+
+case class LeonFatalError() extends Exception

src/main/scala/leon/Main.scala

@@ -157,7 +157,11 @@ object Main {
     // Compute leon pipeline
     val pipeline = computePipeline(ctx.settings)
 
-    // Run pipeline
-    pipeline.run(ctx)(args.toList)
+    try {
+      // Run pipeline
+      pipeline.run(ctx)(args.toList)
+    } catch {
+      case LeonFatalError() => sys.exit(1)
+    }
   }
 }

src/main/scala/leon/Reporter.scala

@@ -53,7 +53,7 @@ class DefaultReporter extends Reporter {
   def errorFunction(msg: Any) = output(reline(errorPfx, msg.toString))
   def warningFunction(msg: Any) = output(reline(warningPfx, msg.toString))
   def infoFunction(msg: Any) = output(reline(infoPfx, msg.toString))
-  def fatalErrorFunction(msg: Any) = { output(reline(fatalPfx, msg.toString)); sys.exit(0) }
+  def fatalErrorFunction(msg: Any) = { output(reline(fatalPfx, msg.toString)); throw LeonFatalError() }
 }
 
 class QuietReporter extends DefaultReporter {

src/main/scala/leon/plugin/AnalysisComponent.scala

@@ -24,7 +24,7 @@ class AnalysisComponent(val global: Global, val pluginInstance: LeonPlugin)
   
   protected def stopIfErrors: Unit = {
     if(reporter.hasErrors) {
-      sys.exit(1)
+      throw LeonFatalError()
     }
   }