Code review comment for lp:~adeuring/charmworld/1199790-last-change-error

I think there is no need for further changes. format_change() is used in templates/charm.pt, but not for first_change or last_change:

              <tr tal:repeat="change charm.changes">
                <td tal:content="structure: format_change(change, charm)"></td>
              </tr>

The second callsite of format_change is in views.feeds._recently_changed(), which in turn is used in recently_changed()
 serving the URL http://staging.jujucharms.com/recently-changed and in recently_changed_feed(), serving the URL http://staging.jujucharms.com/feed/charm-changes. IMHO, an empty string dor the last change does not matter on these pages.