1. After installing odoo
2. Go to the configuration file and
3. change the port,
4. write filter_db = "odoo_12"  (Your current db

5. Restart and reload 
 Note: 
If after creating database and it gives issues:
copy the database name, Add the db name to the dbfilter and then restart
both postgresql and odoo server

@ Ermin Trevisan:

problem is, the database is actually created. I have it in the database selector, as well as any other database I already had (another db on Odoo 8.0, and another on Odoo 10.0). When go to Manage Database -> Erase Database, it's in the list as well - and I can erase it. Of course, it disappears after I do that. But in the meanwhile, after I get the error and before I erase it, the database exists - I even tried to create another database with the same name, and Odoo didn't allow me because of it!

Simply, I can't login into it, and I can't login into any new Odoo 8.0 database (but I am still able to login into the Odoo 8.0 dbs I already created).

EDIT: now, and it didn't happen before, when I try to create a new db, I get the following errors:

Uncaught TypeError: Cannot read property 'apply' of undefined
http://localhost:8069/web/static/src/js/core.js:759

Uncaught TypeError: Cannot read property 'apply' of undefined
http://localhost:8069/web/static/src/js/core.js:769

You can't login to a database which does not exist, because the creation has failed, as described in the log. Please check your Odoo installation and read the docs: https://www.odoo.com/documentation/8.0/setup/install.html