[API-8] Command error messages include exception information

[ejm]

If it is better to merge this into SpongePowered/SpongeAPI#2385 somehow, let me know please!

Right now, when running a command with a parsing error, you receive an error message like this (example is a Parameter.user() encountering a user who has never logged into the server before):

While descriptive, from a player's perspective it offers a lot more information than necessary. In asking about this on Discord, I received the following response from @dualspiral and was asked to add an issue to the tracker about it:

Right now - no. I believe that's a vanilla thing that's going on there as we integrate with Brig quite tightly.

It might become possible later, I have plans to decouple us from Brig a bit for a few reasons, meaning that we take more control over the messages. That's quite a big chunk of work I need to do, and I need to be able to sit down without distraction to do it, and I may not get chance to do so until March.

For the above error message, I would expect something more straight forward like just Could not find user with user name "SlowRiot" without the exception information.

[dualspiral]

If it is better to merge this into SpongePowered/SpongeAPI#2385 somehow, let me know please!

It's not the same issue, don't merge it.

[dualspiral]

#3594 needs to come first.