Base class for cfg exceptions.
Raised if a CLI opt is registered after parsing.
Raised if an opt which doesn’t exist is referenced.
Raised if a group which doesn’t exist is referenced.
Raised if multiple opts with the same name are registered.
Raised if an option is required but no value is supplied by the user.
Raised if an error occurs substituting a variable in an opt value.
Raised if one or more config files are not found.
Raised if there is an error parsing a config file.
Raised if a config file value does not match its opt type.