logilab-database #64792 print instructions left in postgres.py [validation pending]

There are print instructions doing reporting in the functions of the postgres.py module.

Use a logger or give an output stream as a parameter, but change the current behaviour, since there is no way to silence it.

done in1.6.0
load left0.000
closed by#2b49a49b23e2 use logging and not print statements (closes #64792)