Include path in error message for missing router conf, see #3178

akka-actor-tests/src/test/scala/akka/routing/RoutingSpec.scala

@@ -578,9 +578,10 @@ class RoutingSpec extends AkkaSpec(RoutingSpec.config) with DefaultTimeout with
 
   "router FromConfig" must {
     "throw suitable exception when not configured" in {
-      intercept[ConfigurationException] {
-        system.actorOf(Props.empty.withRouter(FromConfig))
-      }.getMessage.contains("application.conf") must be(true)
+      val e = intercept[ConfigurationException] {
+        system.actorOf(Props[TestActor].withRouter(FromConfig), "routerNotDefined")
+      }
+      e.getMessage must include("routerNotDefined")
     }
 
     "allow external configuration" in {

akka-actor/src/main/scala/akka/routing/Routing.scala

@@ -33,7 +33,7 @@ private[akka] class RoutedActorRef(_system: ActorSystemImpl, _props: Props, _sup
     throw new ConfigurationException(
       "Configuration for " + this +
         " is invalid - you can not use a 'BalancingDispatcher' as a Router's dispatcher, you can however use it for the routees.")
-  } else _props.routerConfig.verifyConfig()
+  } else _props.routerConfig.verifyConfig(_path)
 
   override def newCell(old: UnstartedCell): Cell = new RoutedActorCell(system, this, props, supervisor).init(sendSupervise = false)
 
@@ -222,7 +222,7 @@ trait RouterConfig {
   /**
    * Check that everything is there which is needed. Called in constructor of RoutedActorRef to fail early.
    */
-  def verifyConfig(): Unit = ()
+  def verifyConfig(path: ActorPath): Unit = ()
 
   /*
    * Specify that this router should stop itself when all routees have terminated (been removed).
@@ -528,8 +528,8 @@ class FromConfig(val routerDispatcher: String = Dispatchers.DefaultDispatcherId,
 
   def this() = this(Dispatchers.DefaultDispatcherId, Router.defaultSupervisorStrategy)
 
-  override def verifyConfig(): Unit =
-    throw new ConfigurationException("router needs external configuration from file (e.g. application.conf)")
+  override def verifyConfig(path: ActorPath): Unit =
+    throw new ConfigurationException(s"Configuration missing for router [$path] in 'akka.actor.deployment' section.")
 
   def createRoute(routeeProvider: RouteeProvider): Route = null