use our own stream copy instead

lib/private/connector/sabre/file.php

@@ -126,7 +126,7 @@ class File extends Node implements IFile {
 				// because we have no clue about the cause we can only throw back a 500/Internal Server Error
 				throw new Exception('Could not write file contents');
 			}
-			$count = stream_copy_to_stream($data, $target);
+			list($count, ) = \OC_Helper::streamCopy($data, $target);
 			fclose($target);
 
 			// if content length is sent by client: