Comment 4 for bug 857003

Here's the problem as far as I can see. python-mode.el has two definitions
for py-pdbtrack-stack-entry-regexp:

;; pdbtrack constants
(defconst py-pdbtrack-stack-entry-regexp
; "^> \\([^(]+\\)(\\([0-9]+\\))\\([?a-zA-Z0-9_]+\\)()"
  "^> \\(.*\\)(\\([0-9]+\\))\\([?a-zA-Z0-9_<>]+\\)()"
  "Regular expression pdbtrack uses to find a stack trace entry.")

(defconst py-pdbtrack-stack-entry-regexp
  "^(\\([-a-zA-Z0-9_/.]*\\):\\([0-9]+\\)):[ \t]?\\(.*\n\\)"
  "Regular expression pdbtrack uses to find a stack trace entry for pydb.

The debugger outputs program-location lines that look like this:
   (/usr/bin/zonetab2pot.py:15): makePOT")

I'm not sure why there are two defconsts here, but the second one is
overriding the first one. The first one works fine for me, i.e. if I

(setq py-pdbtrack-stack-entry-regexp
      "^> \\(.*\\)(\\([0-9]+\\))\\([?a-zA-Z0-9_<>]+\\)()")

tracking works again.