[Zope] ZPT standard_error_message not finding methods

[Felix Ulrich-Oltean]

Hi

I'm trying to write a standard_error_message page in ZPT and attach it
to my class.

In my class definition I have:

standard_error_message = PageTemplateFile('html/error_page.html',
globals())

and

manage_master = PageTemplateFile('html/master_page.html', globals())

in error_page.html I have:

<p tal:content="exists:container/manage_master" />

Now, this returns true:

http://localhost:8080/sites/myClassInstance/standard_error_message

but this returns false:

http://localhost:8080/sites/myClassInstance/some_nonexistent_page


There are also other methods that are found when calling 
standard_error_message explicitly, but not when it's called as a result
of an  error.

What am I missing about how standard_error_message is called?

TIA

Felix.