BUG #15025: PSQL CLI - inconsistency when both -d and -U supplies a username

The following bug has been logged on the website:

Bug reference: 15025
Logged by: Akos Vandra
Email address: akos(at)elegran(dot)com
PostgreSQL version: 9.5.4
Operating system: Debian
Description:

Repro:

case 1: psql -U other_user -d "postgresql://some_user(at)host/db"

case 2: psql -d "postgresql://some_user(at)host/db" -U other_user

Expectation:

Use whatever is given later:

case 1: log in as user
case 2: log in as other_user

Actual:

case 1: logs in as user
case 2:
- the password prompt asks for the pw of user
- psql uses the password given to log in with other_user
- if the pw is correct for user, or incorrect it displays that the
password is incorrect for other_user
- if the password is correct for other_user, it connects to the db as
other_user

$ psql "postgresql://user(at)host/db" -U other_user
Password for user other_user:
psql: FATAL: password authentication failed for user "user"
FATAL: password authentication failed for user "user"