Minor changes following review of the engine pull request
for this feature;
- Remove the name of the function from the error message
as it's not a debug message.
- Add the valid range to the error message, so that a
user has sufficient information to address the problem.
- Update GoDoc for the function to describe the default
port, and valid port-ranges.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
d7f397c236