The reason for exception OptionAlreadyAdded could be clarified

[tobgu]

If I add an option with short_name="o", name="option", and then another option with short_name="o" and name="another-option" an OptionAlreadyAdded will be thrown since the short name "o" is already in use.

The error message will state that: "another-option is already added", however.

It would be nice if the message could also include the reason for the collision (eg. that the short name is already used).

[jiggersplat]

I just spent an hour figuring out that i can't add an option with short_name="-h" because it is already used by the default help option. OptionAlreadyAdded was a total red herring.