dump the list of available bundles (and extension alaises) if no name is provided

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

Not sure if this should only go into master or if such a small tweak can also go into 2.1 or at least 2.2