SPF: premature end-of-input on private/policy

I've ask a detailed question here: http://serverfault.com/questions/733528/spf-premature-end-of-input-on-private-policy

Basically I have this error:

Nov 3 10:49:05 ns3016726 postfix/spawn[16996]: warning: command /usr/bin/python exit status 1
Nov 3 10:49:05 ns3016726 postfix/smtpd[17991]: warning: premature end-of-input on private/policy while reading input attribute name
Nov 3 10:49:06 ns3016726 postfix/spawn[16998]: warning: command /usr/bin/python exit status 1
Nov 3 10:49:06 ns3016726 postfix/smtpd[17991]: warning: premature end-of-input on private/policy while reading input attribute name
Nov 3 10:49:06 ns3016726 postfix/smtpd[17991]: warning: problem talking to server private/policy: Connection reset by peer

I now since try to run `/usr/bin/python /usr/bin/policyd-spf /etc/postfix-policyd-spf-python/policyd-spf.conf` directly and get:

Traceback (most recent call last):
  File "/usr/bin/policyd-spf", line 36, in <module>
    import spf
ImportError: No module named spf

I then installed pydns and pyspf and now get:

ipaddr module required: http://code.google.com/p/ipaddr-py/
Traceback (most recent call last):
  File "/usr/bin/policyd-spf", line 40, in <module>
    import policydspfsupp
ImportError: No module named policydspfsupp

Any idea of what is going on ?