INT-3516 Fix JPA Build Error

https://build.spring.io/browse/INT-B41-121

build.gradle

@@ -63,15 +63,18 @@ subprojects { subproject ->
 		}
 	}
 
+
 	compileJava {
 		sourceCompatibility = 1.6
 		targetCompatibility = 1.6
 	}
 
 	compileTestJava {
-		sourceCompatibility = 1.8
+		sourceCompatibility = 1.6
+		targetCompatibility = 1.6
 	}
 
+
 	ext {
 		activeMqVersion = '5.10.0'
 		aspectjVersion = '1.8.2'
@@ -243,6 +246,12 @@ project('spring-integration-amqp') {
 
 project('spring-integration-core') {
 	description = 'Spring Integration Core'
+
+	compileTestJava {
+		sourceCompatibility = 1.8
+		targetCompatibility = 1.8
+	}
+
 	dependencies {
 		compile "org.springframework:spring-aop:$springVersion"
 		compile "org.springframework:spring-context:$springVersion"