Implement selection between global config and user settings for duo keys.

src/error.rs

@@ -41,6 +41,8 @@ use regex::Error as RegexErr;
 use reqwest::Error as ReqErr;
 use serde_json::{Error as SerdeErr, Value};
 use std::io::Error as IOErr;
+
+use std::option::NoneError as NoneErr;
 use std::time::SystemTimeError as TimeErr;
 use u2f::u2ferror::U2fError as U2fErr;
 use yubico::yubicoerror::YubicoError as YubiErr;
@@ -73,6 +75,13 @@ make_error! {
     YubiError(YubiErr):   _has_source, _api_error,
 }
 
+// This is implemented by hand because NoneError doesn't implement neither Display nor Error
+impl From<NoneErr> for Error {
+    fn from(_: NoneErr) -> Self {
+        Error::from(("NoneError", String::new()))
+    }
+}
+
 impl std::fmt::Debug for Error {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self.source() {
@@ -118,6 +127,12 @@ impl<E: Into<Error>> MapResult<()> for Result<usize, E> {
     }
 }
 
+impl<S> MapResult<S> for Option<S> {
+    fn map_res(self, msg: &str) -> Result<S, Error> {
+        self.ok_or_else(|| Error::new(msg, ""))
+    }
+}
+
 fn _has_source<T>(e: T) -> Option<T> {
     Some(e)
 }