the constructor now uses text/html as default value for content_type

lib/python/Products/PageTemplates/ZopePageTemplate.py

@@ -103,7 +103,7 @@ class ZopePageTemplate(Script, PageTemplate, Historical, Cacheable,
     security.declareProtected(view_management_screens,
                               'read', 'ZScriptHTML_tryForm')
 
-    def __init__(self, id, text=None, content_type=None, strict=True, output_encoding='utf-8'):
+    def __init__(self, id, text=None, content_type='text/html', strict=True, output_encoding='utf-8'):
         self.id = id
         self.expand = 0                                                               
         self.ZBindings_edit(self._default_bindings)