I'm using Tcl/Tk  8.5.4  here

        print(":::")
        print(_flatten((self._w, cmd)) + self._options(cnf))

produces:
:::
('.3073836300', 'configure', '-yscrollcommand', '3077632332set')
:::
('.3073835564.3073835660', 'configure', '-text', 'Python documentation 
server at\nhttp://localhost:7464/')
>>> Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/local/lib/python3.0/threading.py", line 507, in 
_bootstrap_inner
    self.run()
  File "/usr/local/lib/python3.0/threading.py", line 462, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/local/lib/python3.0/pydoc.py", line 1989, in serve
    DocServer(port, callback).serve_until_quit()
  File "/usr/local/lib/python3.0/pydoc.py", line 1971, in __init__
    self.base.__init__(self, self.address, self.handler)
  File "/usr/local/lib/python3.0/socketserver.py", line 401, in __init__
    self.server_activate()
  File "/usr/local/lib/python3.0/pydoc.py", line 1982, in 
server_activate
    if self.callback: self.callback(self)
  File "/usr/local/lib/python3.0/pydoc.py", line 2072, in ready
    text='Python documentation server at\n' + server.url)
  File "/usr/local/lib/python3.0/tkinter/__init__.py", line 1201, in 
configure
    return self._configure('configure', cnf, kw)
  File "/usr/local/lib/python3.0/tkinter/__init__.py", line 1192, in 
_configure
    self.tk.call(_flatten((self._w, cmd)) + self._options(cnf))
_tkinter.TclError: out of stack space (infinite loop?)