Currently ConfigError is called everywhere as such:
raise ConfigError(( f'static-host-mapping "{host}" address "{hostprops["address"]}"' f'already used in another static-host-mapping'))
This results in output looking like:
static-host-mapping "test2" address "10.0.10.100"already used in another static-host-mapping [[system static-host-mapping]] failed
Given that there's a lot of code with the first pattern, the extra space probably needs to be inserted in the ConfigError object.