* This fix introduces one side-effect: the build parameter is now
validated early, when the service dicionary is first constructed.
That leads to less scary stack traces when the path is not valid.
* The tests for the changes introduced here alter the fixtures
of those (otherwise unrelated) tests that make use of the 'build:'
parameter)
Signed-off-by: Moysés Borges Furtado <moyses.furtado@wplex.com.br>