The stacktrace is not very helpful, unfortunately, but that is not your doing. The original example does not use an "ats" variable but instantiates g with a oneliner, but it hard to see why this could make a difference. Most likely, the code has trouble finding the conf/remote-objects.yaml file, referenced in the conf/remote-graph.properties file.

As an alternative to fiddling with your current code, you could take a look at:

https://github.com/JanusGraph/janusgraph/tree/v0.6.2/janusgraph-examples/example-remotegraph

Best wishes,    Marc