[gnome-builder] rustup: ensure we always have a valid message

[Christian Hergert <chergert src gnome org>]

commit 811a380b6ca4d038b6deb9489f9e569a74b5caf8
Author: Christian Hergert <chergert redhat com>
Date:   Tue Feb 28 13:58:46 2017 -0800

    rustup: ensure we always have a valid message
    
    For some reason, GLib.Error(ex) wasn't wrapping correctly.
    
    See https://bugzilla.gnome.org/show_bug.cgi?id=779358

 plugins/rustup/rustup_plugin/__init__.py |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/plugins/rustup/rustup_plugin/__init__.py b/plugins/rustup/rustup_plugin/__init__.py
index eaa8182..055a384 100644
--- a/plugins/rustup/rustup_plugin/__init__.py
+++ b/plugins/rustup/rustup_plugin/__init__.py
@@ -325,7 +325,7 @@ class RustupInstaller(Ide.Transfer):
         try:
             sub_process = launcher.spawn()
         except Exception as ex:
-            task.return_error(GLib.Error(ex))
+            task.return_error(GLib.Error(message=repr(ex))
 
         sub_process.wait_async(cancellable, self._wait_cb, task)