trezorctl: common exception handling

[matejcik]

Currently, every command has to handle its own exceptions. So most canceled actions throw a stack trace, unless specifically coded against.

That is stupid.

We should have a common exception handler for the subcommands and output nice messages whenever it makes sense.

Also maybe stop for a minute and rethink raising exceptions when an action is canceled?

[cculianu]

Yeah I agree. It's terrible the way it is. Electrum and Electron Cash both have horrible UX's as a result.

[matejcik]

yeah no, that's completely unrelated. these apps are using trezor as a library and can do their own exception handling, so if there's terrible UX that's their problem

this issue is specifically about bad exception handling in trezorctl the CLI tool

[cculianu]

Ok, I'll shut up now. :)