Improve websocket connection error handling.

This commit modifies the error handling for websocket connections to fall
back to returning the status text returned from the server if the
handshake fails and it's not due to an authentication or invalid endpoint.

infrastructure.go

@@ -1037,22 +1037,26 @@ func dial(config *ConnConfig) (*websocket.Conn, error) {
 	url := fmt.Sprintf("%s://%s/%s", scheme, config.Host, config.Endpoint)
 	wsConn, resp, err := dialer.Dial(url, requestHeader)
 	if err != nil {
-		if err == websocket.ErrBadHandshake {
-			// Detect HTTP authentication error status codes.
-			if resp != nil &&
-				(resp.StatusCode == http.StatusUnauthorized ||
-					resp.StatusCode == http.StatusForbidden) {
+		if err != websocket.ErrBadHandshake || resp == nil {
+			return nil, err
+		}
 
-				return nil, ErrInvalidAuth
-			}
+		// Detect HTTP authentication error status codes.
+		if resp.StatusCode == http.StatusUnauthorized ||
+			resp.StatusCode == http.StatusForbidden {
+			return nil, ErrInvalidAuth
+		}
 
-			// The connection was authenticated, but the websocket
-			// handshake still failed, so the endpoint is invalid
-			// in some way.
+		// The connection was authenticated and the status response was
+		// ok, but the websocket handshake still failed, so the endpoint
+		// is invalid in some way.
+		if resp.StatusCode == http.StatusOK {
 			return nil, ErrInvalidEndpoint
 		}
 
-		return nil, err
+		// Return the status text from the server if none of the special
+		// cases above apply.
+		return nil, errors.New(resp.Status)
 	}
 	return wsConn, nil
 }