It is really confusing. The Sonatype project page on github shows this message:
DEPRECATED: This project moved to Eclipse, please follow the link below to find the new sources. http://www.eclipse.org/aether/
The last version published by Sonatype was 1.13. In the Eclipse repo you find versions from 0.9.0 M1 to 1.0.2. But I am not really sure if the Eclipse and the Sonatype packages contain the same classes ...
No, not really - it especially also started failing for openhab1 and openhab2 at the same time.
Maybe the problem is caused by a third party component that has changed its POM and contains a wrong reference.
I have checked the log of the last successful build and tried to compare it with the first one that failed. But I can't see any relevant differences .
I don't know whether it is possible for you to run a test build with a newer Karaf version at least for the failed build step.