starting minidfscluster in tests
Double check your dependencies. This error indicates there are incompatible versions of logging jars on the classpath. I faced a similar problem and had to exclude the log4j-over-slf4j dependency which was introduced by another third-party library.
Upgrading to SLF4J 1.7.6 should solve the issue (we used 1.7.7 though) as the log4j-over-slf4j v1.7.5 is missing AppenderSkeleton.
Quite likely a class is using Log4J somewhere which is invoking AppenderSkeleton, but then the bridge to redirect log4j through slf4j is missing that, and it blows up with the stack trace the poster shows. The release notes on http://www.slf4j.org/news.html describe that this was addressed in 1.7.6.
Logged on Yarn, where we saw the issue: https://issues.apache.org/jira/browse/YARN-2875.