Pulp

When I entered a command using pulp-admin, it just shows me the available commands. It doesn't indicate that the command is bad.

```
❯ pulp-admin blah
Usage: pulp-admin [SUB_SECTION, ..] COMMAND

Available Sections:
auth - manage users, roles and permissions
bindings - search consumer bindings
consumer - display and manage Pulp consumers
docker - manage docker images
event - subscribe to event notifications
iso - manage ISO-related content and features
orphan - find and remove orphaned content units
puppet - manage Puppet-related content and features
repo - list repositories and manage repo groups
rpm - manage RPM-related content and features
server - display info about the server
tasks - list and cancel server-side tasks

Available Commands:
login - login and download a session certificate
logout - deletes the user's session certificate
```

It's helpful to know the available commands but it should (IMO) show something like "blah is not a valid command".