Well, I kind of solved it. After finding this {
https://poi.apache.org/faq.html#faq-N10025 } I downloaded and used
`ooxml-schemas-x.x.jar`instead of `poi-ooxml-schemas-x.x.jar`. Even though
it runs and compiles perfectly with groovy now, I'm still curious about why
it didn't work with `poi-ooxml-schemas-x.x.jar` while the java version did.Cheers.
