Index: /trunk/src/org/openstreetmap/josm/tools/Utils.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/tools/Utils.java	(revision 13471)
+++ /trunk/src/org/openstreetmap/josm/tools/Utils.java	(revision 13472)
@@ -856,5 +856,5 @@
             Logging.debug(join(" ", command));
         }
-        Process p = new ProcessBuilder(command).start();
+        Process p = new ProcessBuilder(command).redirectErrorStream(true).start();
         try (BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream(), StandardCharsets.UTF_8))) {
             StringBuilder all = null;