nexus-staging-maven-plugin fails with `No converter available` and `Unable to make … accessible` and java.base does not "opens java.util" to unnamed module

[mp911de]

rc-release fails with

[ERROR] Failed to execute goal org.sonatype.plugins:nexus-staging-maven-plugin:1.7.0:rc-release (default-cli) on project spring-data-build: Execution default-cli of goal org.sonatype.plugins:nexus-staging-maven-plugin:1.7.0:rc-release failed: No converter available
[ERROR] ---- Debugging information ----
[ERROR] message             : No converter available
[ERROR] type                : java.util.Arrays$ArrayList
[ERROR] converter           : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
[ERROR] message[1]          : Unable to make field protected transient int java.util.AbstractList.modCount accessible: module java.base does not "opens java.util" to unnamed module @3eee08f5
[ERROR] -------------------------------

because of sonatype/nexus-public#110