enforce error message if bundle argument is set

[havvg]

This fixes #180.

The kernel will throw an exception if the bundle could not be found, which also contains the name of the bundle.

[c33s]

#180 (comment)

don't think it really fix the issue you closed. for DX you should really add a helpful exception

 if ($this->bundle == null)
 {
     /*
        something like abort the command and print a helpful message
        - invalid bundlename
        - have you prefixed it with @?
        - do you use powershell? -> quote the command

     */
 }

[havvg]

I tried it, you will receive the error message from the kernel about registering the bundle etc. This should do the trick?

I mean, we can't explicitly hint on any shells the user may use and how he is supposed to interact with it. If your shell requires escaping an @-sign, then so be it, another shell requires escaping other characters, imho that's out of scope.

The @-problem for example will be there for any command he uses within the Symfony eco-system, that utilises the logical names - and actually, the @ isn't required at all, it will be cut off anyways.