Hmm, arq. test enricher has some ancient dependencies. In fact, they rely on CDI 1.0 (and therefore Weld 1.x). Looking closely at the code, it looks like Weld dependency is only needed for tests, for actual impl, CDI will do.
And the test can be re-written to avoid using Weld internal completely assuming we are on CDI 2.0+, here is how - https://github.com/arquillian/arquillian-core/pull/239. With this change you only need to pass in CDI SE impl as test dependency and it will work (still means you need one release for another though, so one has to release without tests passing).
However, the actual issue in Arq. is that it now looks for now outdated annotation[1].
Which I presume is something you have fixed locally? I did check your repos but couldn't find fork of Arq. core. I can fix that as well if you don't have it already.

I've also checked other repos:
 * The core PR[2] you closed was built from Weld's 3.0 branch which is wrong, we need that against current master to be up to date
  - on the PR you said you have something else already, can you push it please? If you don't have it, I can do that as well; I just don't want to duplicate work
 * API PR[3] misses one commit from current master, otherwise it's good

Regards
Matej

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[1] https://github.com/arquillian/arquillian-core/blob/master/testenrichers/cdi/src/main/java/org/jboss/arquillian/testenricher/cdi/CDIInjectionEnricher.java#L37
[2] https://github.com/weld/core/pull/1956
[3] https://github.com/weld/api/pull/91