Index: includes/filerepo/LocalFile.php
===================================================================
--- includes/filerepo/LocalFile.php	(revision 91410)
+++ includes/filerepo/LocalFile.php	(working copy)
@@ -697,7 +697,11 @@
 			if ( strpos( $file, $this->getName() ) !== false ) {
 				$url = $this->getThumbUrl( $file );
 				$urls[] = $url;
-				@unlink( "$dir/$file" );
+				if ( !@unlink( "$dir/$file" ) ) {
+					$err = error_get_last();
+					wfDebugLog( 'purgeThumbnails', __METHOD__ . 'Error deleting' .
+						"$dir/$file: {$err['message']}\n" );
+				}
 			}
 		}