Function strerror 

pub fn strerror(code: igraph_error_t) -> String

igraph’s textual description of a raw error code (igraph_strerror).

use igraph::{error::strerror, ffi};
assert_eq!(strerror(ffi::igraph_error_type_t_IGRAPH_SUCCESS), "No error");
assert!(!strerror(ffi::igraph_error_type_t_IGRAPH_EINVVID).is_empty());