Log error details via Display instead of Debug

src/error.rs

@@ -52,7 +52,7 @@ impl ErrorKind {
     /// A description of this error kind
     pub fn description(self) -> &'static str {
         match self {
-            ErrorKind::Unavailable => "permanent failure or unavailable",
+            ErrorKind::Unavailable => "permanent failure",
             ErrorKind::Transient => "transient failure",
             ErrorKind::NotReady => "not ready yet",
             ErrorKind::Other => "uncategorised",
@@ -123,6 +123,14 @@ impl Error {
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        #[cfg(feature="std")] {
+            if let Some(ref cause) = self.cause {
+                return write!(f, "RNG error [{}]: {}; cause: {}",
+                        self.kind.description(),
+                        self.msg(),
+                        cause);
+            }
+        }
         write!(f, "RNG error [{}]: {}", self.kind.description(), self.msg())
     }
 }

src/lib.rs

@@ -856,9 +856,9 @@ impl<R: SeedableRng> NewRng for R {
 
         trace!("Seeding new RNG");
         new_os().or_else(|e1| {
-            warn!("OsRng failed [falling back to JitterRng]: {:?}", e1);
+            warn!("OsRng failed [falling back to JitterRng]: {}", e1);
             new_jitter().map_err(|_e2| {
-                warn!("JitterRng failed: {:?}", _e2);
+                warn!("JitterRng failed: {}", _e2);
                 // TODO: can we somehow return both error sources?
                 Error::with_cause(
                     ErrorKind::Unavailable,

src/os.rs

@@ -74,7 +74,7 @@ impl Rng for OsRng {
         loop {
             if let Err(e) = self.try_fill_bytes(dest) {
                 if log_err == 0 {
-                    warn!("OsRng failed: {:?}", e);
+                    warn!("OsRng failed: {}", e);
                 }
 
                 if e.kind().should_retry() {