new_contents: from __future__ import print_function
  
  tests = [
      ('demumble', ''),
      ('demumble hello', 'hello\n'),
      ('demumble _Z4funcPci', 'func(char*, int)\n'),
      ('demumble ?Fx_i@@YAHP6AHH@Z@Z', 'int __cdecl Fx_i(int (__cdecl*)(int))\n'),
  ]
  
  import os, subprocess
  for t in tests:
      cmd = t[0].split()
      # Assume that demumble is next to this script.
      cmd[0] = os.path.join(os.path.dirname(__file__) or '.', cmd[0])
      out = subprocess.check_output(cmd)
      if out != t[1]:
        print("`%s`: Expected '%s', got '%s'" % (t[0], t[1], out))
  
subject: add simplisitc test for demumble