Add PHPDoc for thrown exception

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

lib/private/Files/ObjectStore/Swift.php

@@ -86,6 +86,7 @@ class Swift implements IObjectStore {
 	 * @param string $urn the unified resource name used to identify the object
 	 * @return resource stream with the read data
 	 * @throws \Exception from openstack lib when something goes wrong
+	 * @throws NotFoundException if file does not exist
 	 */
 	public function readObject($urn) {
 		try {

lib/public/Files/ObjectStore/IObjectStore.php

@@ -23,6 +23,8 @@
  */
 namespace OCP\Files\ObjectStore;
 
+use OCP\Files\NotFoundException;
+
 /**
  * Interface IObjectStore
  *
@@ -41,6 +43,7 @@ interface IObjectStore {
 	 * @param string $urn the unified resource name used to identify the object
 	 * @return resource stream with the read data
 	 * @throws \Exception when something goes wrong, message will be logged
+	 * @throws NotFoundException if file does not exist
 	 * @since 7.0.0
 	 */
 	public function readObject($urn);