From 488519ef89b22bacc937db7bb9651079e6263e0a Mon Sep 17 00:00:00 2001
From: Fabien Meghazi <fme@odoo.com>
Date: Wed, 10 May 2017 17:01:11 +0200
Subject: [PATCH] [IMP] assetsbundles: show css compiler returncode if no
 output

---
 odoo/addons/base/ir/ir_qweb/assetsbundle.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/odoo/addons/base/ir/ir_qweb/assetsbundle.py b/odoo/addons/base/ir/ir_qweb/assetsbundle.py
index 415be062a10..ac7c04fba38 100644
--- a/odoo/addons/base/ir/ir_qweb/assetsbundle.py
+++ b/odoo/addons/base/ir/ir_qweb/assetsbundle.py
@@ -399,7 +399,10 @@ class AssetsBundle(object):
             return ''
         result = compiler.communicate(input=source.encode('utf-8'))
         if compiler.returncode:
-            error = self.get_preprocessor_error(''.join(result), source=source)
+            cmd_output = ''.join(result)
+            if not cmd_output:
+                cmd_output = "Process exited with return code %d\n" % compiler.returncode
+            error = self.get_preprocessor_error(cmd_output, source=source)
             _logger.warning(error)
             self.css_errors.append(error)
             return ''