manage_page_header when called through a ZPT seems to acquire

the management_page_property from the Application object instead
from the current context object

lib/python/Products/PageTemplates/pt/ptEdit.pt

 
-<h1 tal:replace="structure python: context.manage_page_header(management_page_charset='utf-8')">Header</h1>
+<h1 tal:replace="structure python: context.manage_page_header(management_page_charset=context.pt_encoding())">Header</h1>
 <h2 tal:define="manage_tabs_message options/manage_tabs_message | nothing"
     tal:replace="structure context/manage_tabs">Tabs</h2>