[gen] Allow to have data change events that contain comments.

gen/mixins/__init__.py

@@ -177,8 +177,7 @@ class BaseMixin:
                 history.append(event)
         self.workflow_history['appy'] = tuple(history)
         appy = self.appy()
-        self.log('data change event deleted for %s (UID=%s).' % \
-                 (appy.klass.__name__, appy.uid))
+        self.log('data change event deleted for %s.' % appy.uid)
         self.goto(self.getUrl(rq['HTTP_REFERER']))
 
     def onLink(self):

gen/wrappers/__init__.py

@@ -370,7 +370,7 @@ class AbstractWrapper(object):
         <td if="isDataChange">
          <!-- Display the previous values of the fields whose value were
               modified in this change. -->
-         <table class="appyChanges" width="100%">
+         <table class="appyChanges" width="100%" if="event['changes']">
           <tr>
            <th align=":dleft" width="30%">:_('modified_field')</th>
            <th align=":dleft" width="70%">:_('previous_value')</th>
@@ -384,6 +384,8 @@ class AbstractWrapper(object):
            <td>::change[1][0]</td>
           </tr>
          </table>
+         <!-- There may also be a comment, too -->
+         <x if="rhComments">::zobj.formatText(rhComments)</x>
         </td>
        </tr>
       </table>