improve text gathering

ERP5Diff.py

@@ -348,13 +348,7 @@ class ERP5Diff:
     """
       Aggregate child text nodes of an element into a single string.
     """
-    text = ''
-    if not self._hasChildren(element):
-      return element.text
-    for child in element:
-      if type(child) == etree._Element:
-        text += child.text
-    return text
+    return '%s' % element.xpath('string(text())')
 
   def _removeStrictEqualsSubNodeList(self, old_list, new_list):
     """Remove inside list all elements which are similar