Certbot-auto: unable to check for updates

[er0k]

I have three machines running Ubuntu 12.04.5 with python 2.7.3, and on two of them, certbot-auto works great, but on the 3rd machine I get this warning:

sudo certbot-auto --help
Traceback (most recent call last):
  File "/usr/lib/python2.7/site.py", line 562, in <module>
    main()
  File "/usr/lib/python2.7/site.py", line 544, in main
    known_paths = addusersitepackages(known_paths)
  File "/usr/lib/python2.7/site.py", line 271, in addusersitepackages
    user_site = getusersitepackages()
  File "/usr/lib/python2.7/site.py", line 246, in getusersitepackages
    user_base = getuserbase() # this will also set USER_BASE
  File "/usr/lib/python2.7/site.py", line 236, in getuserbase
    USER_BASE = get_config_var('userbase')
  File "/usr/lib/python2.7/sysconfig.py", line 577, in get_config_var
    return get_config_vars().get(name)
  File "/usr/lib/python2.7/sysconfig.py", line 476, in get_config_vars
    _init_posix(_CONFIG_VARS)
  File "/usr/lib/python2.7/sysconfig.py", line 337, in _init_posix
    makefile = _get_makefile_filename()
  File "/usr/lib/python2.7/sysconfig.py", line 331, in _get_makefile_filename
    return os.path.join(get_path('platstdlib').replace("/usr/local","/usr",1), "config" + (sys.pydebug and "_d" or ""), "Makefile")
AttributeError: 'module' object has no attribute 'pydebug'
WARNING: unable to check for updates.

  certbot-auto [SUBCOMMAND] [options] [-d domain] [-d domain] ...

Certbot can obtain and install HTTPS/TLS/SSL certificates.  By default,
it will attempt to use a webserver both for obtaining and installing the
<snip>

pip says pydebug is installed and the latest version. I have tried

apt-get install --reinstall python2.7

but it didn’t help, still get the same error.

I can’t figure out why this is only happening on the one box. Can anyone help?