Do not raise an exception if a given plugin manager is not defined.

src/Listener/ServiceListener.php

@@ -199,10 +199,8 @@ public function onLoadModulesPost(ModuleEvent $e)
 
             if (! $sm['service_manager'] instanceof ServiceManager) {
                 if (! $this->defaultServiceManager->has($sm['service_manager'])) {
-                    throw new Exception\RuntimeException(sprintf(
-                        'Could not find a valid ServiceManager for %s',
-                        $sm['service_manager']
-                    ));
+                    // No plugin manager registered by that name; nothing to configure.
+                    continue;
                 }
 
                 $instance = $this->defaultServiceManager->get($sm['service_manager']);

test/Listener/ServiceListenerTest.php

@@ -398,4 +398,33 @@ public function testListenerCanOverrideServicesInServiceManagers()
         $this->assertEquals(['foo' => 'bar'], $services->get('config'), 'Config service was not overridden');
         $this->assertInstanceOf(stdClass::class, $services->get('foo'), 'Foo service was not overridden');
     }
+
+    public function testOnLoadModulesPostShouldNotRaiseExceptionIfNamedServiceManagerDoesNotExist()
+    {
+        $services = new ServiceManager();
+        $services->setService('config', []);
+        $listener = new ServiceListener($services);
+        $listener->addServiceManager(
+            'UndefinedPluginManager',
+            'undefined',
+            TestAsset\UndefinedProviderInterface::class,
+            'getUndefinedConfig'
+        );
+
+        $module = new TestAsset\ServiceProviderModule([]);
+
+        $event          = new ModuleEvent();
+        $configListener = new ConfigListener();
+        $event->setConfigListener($configListener);
+
+        $event->setModule($module);
+        $listener->onLoadModule($event);
+
+        try {
+            $listener->onLoadModulesPost($event);
+            $this->assertFalse($services->has('UndefinedPluginManager'));
+        } catch (\Exception $e) {
+            $this->fail('Exception should not be raised when encountering unknown plugin manager services');
+        }
+    }
 }

test/Listener/TestAsset/UndefinedProviderInterface.php

@@ -0,0 +1,13 @@
+<?php
+/**
+ * @link      http://github.com/zendframework/zend-modulemanager for the canonical source repository
+ * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license   http://framework.zend.com/license/new-bsd New BSD License
+ */
+
+namespace ZendTest\ModuleManager\Listener\TestAsset;
+
+interface UndefinedProviderInterface
+{
+    public function getUndefinedConfig();
+}