The get_file_upload_error() function is missing the following error codes:

UPLOAD_ERR_NO_TMP_DIR => 'Missing a temporary folder.',
UPLOAD_ERR_CANT_WRITE => 'Failed to write file to disk.',
UPLOAD_ERR_EXTENSION => 'File upload stopped by extension.',

(see http://www.php.net/manual/en/features.file-upload.errors.php)