Ian the following PR addresses these concerns:
https://github.com/geoserver/geoserver/pull/4186
I have isolated some community modules into profiles, including the
gs-script-py module (which is now off by default as theSNAPSHOT required is
no longer published anywhere after the repository change).
Just focusing on geoserver-devel here:
The email "*2.17-RC available for testing*" has the details, but TLDR:
1. build_release.sh failed to find the assembly (and used its fallback plan
for older branches which does not include api folder)
2. Several extension bundles to fix, notably
geoserver-2.
