Add hasRedirect() method for OAuthServerException

Resolves #694.

src/Exception/OAuthServerException.php

@@ -273,6 +273,19 @@ class OAuthServerException extends \Exception
         return $headers;
     }
 
+    /**
+     * Returns whether the exception includes a redirect, since
+     * getHttpStatusCode() doesn't return a 302 when there's a
+     * redirect enabled. This helps when you want to override local
+     * error pages but want to let redirects through.
+     *
+     * @return bool
+     */
+    public function hasRedirect()
+    {
+        return $this->redirectUri !== null;
+    }
+
     /**
      * Returns the HTTP status code to send when the exceptions is output.
      *