bug#15295: python mode slow to unusable

[Alex V . Koval]

For me this is happen as well. Emacs, starting from version 24.3 became
so slow in Python mode that I had to tell all developers at our company
to use version 24.2 until I sorted this out.

Sit today and started trying various emacs versions, and calling
different functions. The suggested test case from original author above,
runs with this benchmark:

(7.3956507 53 1.8788885930000063)

In fact, when I enable which-function-mode and just try to open
one of our project files, it reads it 62 seconds. *Same* file opened
with emacs 24.2 reads < 1second. 

Same thing happens when I try to call 'help-imenu' - 46 seconds. In
emacs 24.2 - less then 1 second.

I have this bug in version 24.3 and 'bzr' current:

 * Emacs branch: trunk
 * Revision: 114814
 * Emacs version number: 24.3.50

Please tell me what additional information should I provide.
Not very big expert in Lisp but may try to debug it more
to detail.

WBR, Alex