Is your database server localhost and you are using the command #sudo -u odoo psql -h localhost to connect to it?
From the error message, it seems that the peer authentication is used for user odoo .
In this case, you don't have to set the password. (Password will not be used)
Do you want to keep using peer authentication or use password(md5) authentication?
In the former case, you should start pgadmin as odoo user and leave the Host field blank so that pgadmin connects using the local Unix socket rather than TCP.
In the latter case, you should change the pb_hba.conf like the following to let odoo user use the md5 authentication.
local your-database odoo md5