print the schemaResource description info when schemaResource not exist

Author: dugenkui03

spring-graphql/src/main/java/org/springframework/graphql/execution/DefaultGraphQlSourceBuilder.java

@@ -184,7 +184,7 @@ private void registerDefaultTypeResolver(TypeDefinitionRegistry registry, Runtim
 
 	private TypeDefinitionRegistry parseSchemaResource(Resource schemaResource) {
 		Assert.notNull(schemaResource, "'schemaResource' not provided");
-		Assert.isTrue(schemaResource.exists(), "'schemaResource' does not exist");
+		Assert.isTrue(schemaResource.exists(), "'schemaResource' must exist: " + schemaResource);
 		try {
 			try (InputStream inputStream = schemaResource.getInputStream()) {
 				return new SchemaParser().parse(inputStream);