Peer authentication failed for user "odoo"
This helped me.

sudo nano /etc/postgresql/9.3/main/pg_hba.conf

then add

local all odoo trust

then restart postgres

sudo service postgresql restart
I'm on Odoo 9, I have an issue when lunching odoo server $odoo.py -r odoo -w password, the localhost:8069 doesn't load and I get an error on terminal "Peer authentication failed for user "odoo"". 
I already created a user "odoo" on postgres.
When lunching $odoo.py I can load the odoo page on browser but I can't create database (as default user).
It was working and i already created database but when I logged out I couldn't connect to my database account anymore.
Any ideas ?