[FIX] qweb: correctly display qweb error message

When compiling the qweb template, if an error occurs, an error message is
displayed with the corresponding failed node.

This messsage was not always correct because the node is modified in place
during the compilation proccess.

The template is now re-read before displaying the error.

odoo/addons/base/models/qweb.py

@@ -329,6 +329,7 @@ class QWeb(object):
             raise e
         except Exception as e:
             path = _options['last_path_node']
+            element, document = self.get_template(template, options)
             node = element.getroottree().xpath(path)
             raise QWebException("Error when compiling AST", e, path, node and etree.tostring(node[0], encoding='unicode'), name)