Google Cloud dependencies are pulling in multiple incompatible versions of Guava. Most depend on newer versions of Guava like com.google.guava:guava:20, but others are pulling in com.google.guava:guava-jdk5:17.0. When I miss excluding that ancient jdk5 version from somewhere I end up with a bunch of classloader issues like:

java.lang.NoSuchMethodError: com.google.common.base.Preconditions.checkArgument(ZLjava/lang/String;J)V

For some reason I see this mostly with Cloud KMS (com.google.apis:google-api-services-cloudkms), but it actually appears to be coming from com.google.api-client:google-api-client:1.23.0. See http://mvnrepository.com/artifact/com.google.api-client/google-api-client/1.23.0 for example.

I'd be happy to contribute a PR myself, but I can't seem to find the right repo.