Fixing this with createuser won’t work. Per the man page for createuser, it says that login will fail if you really need a password and set --no-password. createuser just creates a user. It does not decide how the user will have to authenticate.
Authentication is handled mainly in pg_hba.conf, which decides whether or not to require passwords at login. I’ve never run PostgreSQL on OS X. On Linux, my distro’s stock conf looks like this:
# TYPE DATABASE USER CIDR-ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all ident
# IPv4 local connections:
host all all 127.0.0.1/32 trust
# IPv6 local connections:
host all all ::1/128 trust
Make sure you have something like the first line for for development access. Note: psql will try to connect with a unix socket if there is no --host option set. The second line would be used if you try to connect with psql --host localhost