The Schema loader is currently specified to not require a schema source to be present, in other words, it is not required to report an exception when it fails to parse a schema source. This situation happens when a source returned by a resolver contains invalid schema document or incorrect path to the document. The exception returned by the parser then is not reported as an error but a warning.

It also happens that the internal ErrorHandler did not implement the "warning" method. As a result, nothing is reported back, no error and no warning either.

Reproduce:
    Try loading a schema that imports another, use a resolve to return an invalid source path. A schema object will be created with no error.