bug#27712: 26.0.50; ffap in python-mode

[kootenpv]

In python-mode, with elpy loaded (seems to have no effect), nothing has
effect. I'm just doing "ido-find-file". The trace shows ffap in there.

This is the debugger info:

Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
  replace-regexp-in-string("\\`\\^" "" nil)
  (concat "\015?\n?" (replace-regexp-in-string "\\`\\^" "" 
python-shell--prompt-calculated-input-regexp) "\\'")
  (string-match (concat "\015?\n?" (replace-regexp-in-string "\\`\\^" "" 
python-shell--prompt-calculated-input-regexp) "\\'") output)
  (let ((debug-on-error t)) (string-match (concat "\015?\n?" 
(replace-regexp-in-string "\\`\\^" "" 
python-shell--prompt-calculated-input-regexp) "\\'") output))
  python-shell-comint-end-of-output-p("\n")
  python-shell-output-filter("\n")
  comint-output-filter(#<process python> "\n")
  accept-process-output(#<process python>)
  python-shell-send-string-no-output("\ndef __FFAP_get_module_path(objstr):\n   
 try:\n        import inspect\n        import os.path\n        # NameError 
exceptions are delayed until this point.\n        obj = eval(objstr)\n        
module = inspect.getmodule(obj)\n        filename = module.__file__\n        
ext = os.path.splitext(filename)[1]\n        if ext in ('.pyc', '.pyo'):\n      
      # Point to the source file.\n            filename = filename[:-1]\n       
 if os.path.exists(filename):\n            return filename\n        return ''\n 
   except:\n        return ''\nprint (__FFAP_get_module_path('''import'''))" 
#<process python>)
  python-ffap-module-path("import")
  ffap-file-at-point()
  ffap-guesser()
  ido-file-internal(raise-frame)
  ido-find-file()
  funcall-interactively(ido-find-file)
  call-interactively(ido-find-file nil nil)
  command-execute(ido-find-file)



In GNU Emacs 26.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.16)
 of 2017-07-01 built on archbook
Repository revision: 7618d29db36396fbd736672cadaca641186c1dc5
Windowing system distributor 'The X.Org Foundation', version 11.0.11903000
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Configured using:
 'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
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 CPPFLAGS=-D_FORTIFY_SOURCE=2
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Important settings:
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Major mode: Debugger

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