docs: def _psql_cmd(*args, **kwargs):
      '''
      Return string with fully composed psql command.
  
      Accepts optional keyword arguments: user, host, port and maintenance_db,
      as well as any number of positional arguments to be added to the end of
      the command.
      '''
      (user, host, port, maintenance_db) = _connection_defaults(
          kwargs.get('user'),
          kwargs.get('host'),
          kwargs.get('port'),
          kwargs.get('maintenance_db'))
      _PSQL_BIN = _find_pg_binary('psql')
      cmd = [_PSQL_BIN,
             '--no-align',
             '--no-readline',
             '--no-psqlrc',
             '--no-password']  # Never prompt, handled in _run_psql.
      if user:
          cmd += ['--username', user]
      if host:
          cmd += ['--host', host]
      if port:
          cmd += ['--port', six.text_type(port)]
      if not maintenance_db:
          maintenance_db = 'postgres'
      cmd.extend(['--dbname', maintenance_db])
      cmd.extend(args)
      return cmd