Drush cc message is confusing

Eh, I guess this is more of a feature request.

Here's a simple adjustment to improve the error message when there is no bootstrapped site.

$ drush cc djlae
'djlae' cache is not a valid cache type. There may be more cache     [error]
types available if you select a working Drupal site.
$ drush cc css-js
'css-js' cache requires a working Drupal site to operate on. Use the [error]
--root and --uri options, or a site @alias, or cd to a directory
containing a Drupal settings.php file.
$ drush @site cc aslje
'aslje' cache is not a valid cache type.                             [error]

It says this:

$ drush cc druAsh
'druAsh' cache is not a valid cache type. There may be more cache     [error]
types available if you select a working Drupal site.

There's no good way to tell the difference between a typo and a type that might be available via a hook, so the message says that there "may be more" cache types. If you prefer, the message above could be removed, and left in its current short form unless a user exactly types a cache type that is known to be available when a Drupal site is bootstrapped.

Committed to 8.x-6.x and 7.x-5.x.