Change exit calls to throwing an exception

This way the error won't be fatal in a unit test

lib/app.php

@@ -839,9 +839,8 @@ class OC_App{
 					OC_Hook::emit('update', 'success', 'Updated '.$info['name'].' app');
 				}
 				catch (Exception $e) {
-					echo 'Failed to upgrade "'.$app.'". Exception="'.$e->getMessage().'"';
 					OC_Hook::emit('update', 'failure', 'Failed to update '.$info['name'].' app: '.$e->getMessage());
-					die;
+					throw new RuntimeException('Failed to upgrade "'.$app.'". Exception="'.$e->getMessage().'"');
 				}
 				OC_Appconfig::setValue($app, 'installed_version', OC_App::getAppVersion($app));
 			}

lib/files.php

@@ -62,7 +62,7 @@ class OC_Files {
 			$zip = new ZipArchive();
 			$filename = OC_Helper::tmpFile('.zip');
 			if ($zip->open($filename, ZIPARCHIVE::CREATE | ZIPARCHIVE::OVERWRITE)!==true) {
-				exit("cannot open <$filename>\n");
+				throw new Exception("cannot open '$filename'\n");
 			}
 			foreach ($files as $file) {
 				$file = $dir . '/' . $file;
@@ -93,7 +93,7 @@ class OC_Files {
 			$zip = new ZipArchive();
 			$filename = OC_Helper::tmpFile('.zip');
 			if ($zip->open($filename, ZIPARCHIVE::CREATE | ZIPARCHIVE::OVERWRITE)!==true) {
-				exit("cannot open <$filename>\n");
+				throw new Exception("cannot open '$filename'\n");
 			}
 			$file = $dir . '/' . $files;
 			self::zipAddDir($file, $zip);

lib/helper.php

@@ -176,8 +176,7 @@ class OC_Helper {
 		}elseif( file_exists( OC::$SERVERROOT."/core/img/$image" )) {
 			return OC::$WEBROOT."/core/img/$image";
 		}else{
-			echo('image not found: image:'.$image.' webroot:'.OC::$WEBROOT.' serverroot:'.OC::$SERVERROOT);
-			die();
+			throw new RuntimeException('image not found: image:'.$image.' webroot:'.OC::$WEBROOT.' serverroot:'.OC::$SERVERROOT);
 		}
 	}