[BUG] Special characters in the password break psql command

Tag/version of Container Images
0.5.3

We do use a password generator to make database passwords. This time password had a % sign inside it.

Container initialisation started to fail with the:

psql: error: invalid percent-encoded token: "AmJawatHen%queifJof5"
Postgres is unavailable - sleeping
psql: error: invalid percent-encoded token: "AmJawatHen%queifJof5"
Postgres is unavailable - sleeping
psql: error: invalid percent-encoded token: "AmJawatHen%queifJof5"
Postgres is unavailable - sleeping
psql: error: invalid percent-encoded token: "AmJawatHen%queifJof5"
Postgres is unavailable - sleeping

The same message was both mailman-core and mailman-web containers, so it looks like in the wait_for_postgres function.

I'm not sure what would be the best fix here, except, maybe, a special note in the documentation that % sign has to be escaped, if present in the password.

Start at the wait_for_postgres function used during initialization of the mailman-core and mailman-web containers, and reproduce the failure with a PostgreSQL password containing a percent sign. Done means container initialization succeeds and PostgreSQL readiness checks work with that password.