Return an Error instead of panic if sync Client cannot startup runtime.

The timeout is also increased to 10 seconds from 5.

Closes #392

src/client.rs

@@ -462,14 +462,6 @@ impl ClientHandle {
             };
 
             let work = rx.for_each(move |(req, tx)| {
-                /*
-                let tx: oneshot::Sender<::Result<async_impl::Response>> = tx;
-                let task = client.execute(req)
-                    .then(move |r| {
-                        trace!("result received: {:?}", r);
-                        tx.send(r).map_err(|_| ())
-                    });
-                    */
                 let mut tx_opt: Option<oneshot::Sender<::Result<async_impl::Response>>> = Some(tx);
                 let mut res_fut = client.execute(req);
 
@@ -508,10 +500,15 @@ impl ClientHandle {
                 .expect("runtime unexpected error");
         }));
 
-        // Wait up to 5 seconds for the background thread to be spawned.
+        // Wait some seconds for the background thread to be spawned.
         // More than that and something bad is up!
-        wait::timeout(spawn_rx, Some(Duration::from_secs(5)))
+        match wait::timeout(spawn_rx, Some(Duration::from_secs(10))) {
-            .expect("runtime thread cancelled")?;
+            Ok(Ok(())) => (),
+            Ok(Err(err)) => return Err(err),
+            Err(wait::Waited::Err(_/*mpsc::Canceled*/)) |
+            Err(wait::Waited::TimedOut) => return Err(::error::runtime_startup()),
+        }
+
 
         let inner_handle = Arc::new(InnerClientHandle {
             tx: Some(tx),

src/error.rs

@@ -147,7 +147,8 @@ impl Error {
             Kind::TooManyRedirects |
             Kind::RedirectLoop |
             Kind::ClientError(_) |
-            Kind::ServerError(_) => None,
+            Kind::ServerError(_) |
+            Kind::RuntimeStartupFailure => None,
         }
     }
 
@@ -250,6 +251,7 @@ impl fmt::Display for Error {
                 f.write_str("Server Error: ")?;
                 fmt::Display::fmt(code, f)
             }
+            Kind::RuntimeStartupFailure => f.write_str("Client runtime failed to start"),
         }
     }
 }
@@ -275,6 +277,7 @@ impl StdError for Error {
             Kind::RedirectLoop => "Infinite redirect loop",
             Kind::ClientError(_) => "Client Error",
             Kind::ServerError(_) => "Server Error",
+            Kind::RuntimeStartupFailure => "Client runtime failed to start",
         }
     }
 
@@ -298,7 +301,8 @@ impl StdError for Error {
             Kind::TooManyRedirects |
             Kind::RedirectLoop |
             Kind::ClientError(_) |
-            Kind::ServerError(_) => None,
+            Kind::ServerError(_) |
+            Kind::RuntimeStartupFailure => None,
         }
     }
 }
@@ -323,6 +327,7 @@ pub(crate) enum Kind {
     RedirectLoop,
     ClientError(StatusCode),
     ServerError(StatusCode),
+    RuntimeStartupFailure,
 }
 
 
@@ -489,6 +494,10 @@ pub(crate) fn url_bad_scheme(url: Url) -> Error {
     Error::new(Kind::UrlBadScheme, Some(url))
 }
 
+pub(crate) fn runtime_startup() -> Error {
+    Error::new(Kind::RuntimeStartupFailure, None)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;