some aditional feedback during database upgrade

lib/base.php

@@ -156,7 +156,11 @@ class OC{
 			$installedVersion=OC_Config::getValue('version','0.0.0');
 			$currentVersion=implode('.',OC_Util::getVersion());
 			if (version_compare($currentVersion, $installedVersion, '>')) {
-				OC_DB::updateDbFromStructure(OC::$SERVERROOT.'/db_structure.xml');
+				$result=OC_DB::updateDbFromStructure(OC::$SERVERROOT.'/db_structure.xml');
+				if(!$result){
+					echo 'Error while upgrading the database';
+					die();
+				}
 				OC_Config::setValue('version',implode('.',OC_Util::getVersion()));
 			}
 

lib/db.php

@@ -361,6 +361,11 @@ class OC_DB {
 		$content = file_get_contents( $file );
 		
 		$previousSchema = self::$schema->getDefinitionFromDatabase();
+		if (PEAR::isError($previousSchema)) {
+			$error = $previousSchema->getMessage();
+			OC_Log::write('core','Failed to get existing database structure for upgrading ('.$error.')',OC_Log::FATAL);
+			return false;
+		}
 
 		// Make changes and save them to a temporary file
 		$file2 = tempnam( get_temp_dir(), 'oc_db_scheme_' );