[FIX] ir_attachment: write traceback to logs when upload fail

When the upload of an attachment failed,
e.g. for access rights reasons,
the traceback wasn't written or returned anywhere,
preventing the easy debugging.

opw-640242

addons/web/controllers/main.py

@@ -1168,6 +1168,7 @@ class Binary(http.Controller):
             }
         except Exception:
             args = {'error': "Something horrible happened"}
+            _logger.exception("Fail to upload attachment %s" % ufile.filename)
         return out % (simplejson.dumps(callback), simplejson.dumps(args))
 
     @http.route([