OsgiServiceUtil: clarify exception message when no matching references were found

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1684446 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/sling/testing/mock/osgi/OsgiServiceUtil.java b/src/main/java/org/apache/sling/testing/mock/osgi/OsgiServiceUtil.java
index 82c722c..2c427e5 100644
--- a/src/main/java/org/apache/sling/testing/mock/osgi/OsgiServiceUtil.java
+++ b/src/main/java/org/apache/sling/testing/mock/osgi/OsgiServiceUtil.java
@@ -310,7 +310,7 @@
             boolean isOptional = (reference.getCardinality() == ReferenceCardinality.OPTIONAL_UNARY || reference
                     .getCardinality() == ReferenceCardinality.OPTIONAL_MULTIPLE);
             if (!isOptional) {
-                throw new ReferenceViolationException("Unable to inject mandatory reference '" + reference.getName() + "' for class " + targetClass.getName());
+                throw new ReferenceViolationException("Unable to inject mandatory reference '" + reference.getName() + "' for class " + targetClass.getName() + " : no matching services were found.");
             }
         }