could not create IPv6 socket: Address family not supported by protocol

if you get this error and sure that it is not from kernel or other stuff.
You should check pg_hba.conf file
if you wrote wrong entry on that file, i get the same error. May be this will help you.

ex:
wrong entry:

host    all             replication     192.168.3.140        trust #did you notice i forget to give mask /32. when i put and restart postgresql, it start without error.