title: Postgresql Docker role does not exist
body: <p>I downloaded the docker container for postgres: <a href="https://hub.docker.com/r/library/postgres/" rel="noreferrer">https://hub.docker.com/r/library/postgres/</a>, and did the following:</p>
  
  <pre><code>$ docker run --name satgres -e POSTGRES_PASSWORD=mysecretpassword -d -p 5432:5432 postgres
  satgres | "docker-entrypoint.s…" | 5 seconds ago | Up 6 seconds | 0.0.0.0:5432-&gt;5432/tcp | satgres
  $ docker exec -it c8f1b22cc41e /bin/bash        
  # psql -U postgres
  psql (10.1)
  postgres=# CREATE DATABASE mytest;
  postgres=# \password postgres
  postgres=# CREATE ROLE ming WITH LOGIN PASSWORD 'pass1234';
  postgres=# ALTER ROLE ming CREATEDB;
  postgres=# CREATE DATABASE sjk;
  postgres=# GRANT ALL PRIVILEGES ON DATABASE youtube TO ming;
  postgres=# \connect sjk
  youtube=# ALTER ROLE ming lOGIN;  
  </code></pre>
  
  <p>My plan is to use this database on docker with Django, so first want to check I can connect, but I cant.</p>
  
  <pre><code>$ psql -h localhost -p 5432 -U postgres
  $ psql: FATAL:  role "postgres" does not exist
  $ psql -h localhost -p 5432 -U ming
  $ psql: FATAL:  role "ming" does not exist
  </code></pre>
  
  <p>I do the same with PSequal.app, says the same thing,
  Im running on Mac High Sierra. </p>
  
  <p>Why am I getting this error? The role exists, or at least it seems it to me...</p>