My initial description doesn't state the actual observable problem very
clearly: the problem is that the browser gets stuck instead of
displaying the page, writing something along the lines of "Transferring
data from localhost". After many seconds it times out. Aborting the
request in Firefox causes the page to be displayed.

Also forgot to mention that it's possible to work around this by
explicitly removing all circular references after the base class'
__init__ method - so for the attached example a work-around is
"self.dummy = None" as the last line of the __init__ method.