XSD step requires Saxon-EE

[JDziurlaj]

When using Calabash with an XProc Pipeline that uses validate-with-xml-schema, I get the error Error: Validation requires Saxon EE. Fair enough, schema validation with Saxon requires EE. However, schema validation is a common use case, so I would ask that another validator be possible to use in its place (parameterize).

[ndw]

If you don't have EE, it's supposed to use Xerces automatically. There are some compromises, the Xercies API doesn't support quite the same level of flexibility in providing schemas and, while it validates, it doesn't return a PSVI for subsequent steps. It's also a bit slower as the only way to make it work is to serialize the input and run it through Xerces as a parser.

I suppose I might have broken that feature, though I thought I tested it recently. I'll take a look asap.