Display real errors for failed challenges

[Globulopolis]

Hi! I've found this https://github.com/kelunik/acme-client/blob/master/src/Commands/Issue.php#L101-L107 in code. Maybe it's better to throw an real exception message instead of Issuance failed, not all challenges could be solved. ? Because in current implementation foreach is useless.

[kelunik]

The current implementation shows the error messages to the console, why is that useless? Could you clarify?

[Globulopolis]

I meant an extended error description. Not a predefined value.

[kelunik]

@Globulopolis The foreach about the previous errors should give more information. We could merge them into the exception message, but the information that's given to the end-user will be almost the same.