It would be good to get @bcail's verification of this PR.

The test looks good to me, although I haven't actually run the new code. I guess for testing the PR I'd need to clone Mike's repo & use the maven system? How often are new jars created?

@bcail, download the executable jar from here:
https://s3.amazonaws.com/aw-misc/migration-utils-4.2.1-SNAPSHOT-driver.jar

The readme may also be helpful:
https://github.com/fcrepo4-labs/migration-utils/blob/master/README.md

I cloned Mike's repo & ran it on my data with the mvn command. I'm getting the following (different) error:
DEBUG 15:26:03.716 (BasicObjectVersionHandler) Considering changed datastream version RELS-INT.0
[WARNING]
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:293)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at org.fcrepo.migration.handlers.BasicObjectVersionHandler.updateResourceProperties(BasicObjectVersionHandler.java:491)
at org.fcrepo.migration.handlers.BasicObjectVersionHandler.migrateRelsInt(BasicObjectVersionHandler.java:439)
at org.fcrepo.migration.handlers.BasicObjectVersionHandler.processObjectVersions(BasicObjectVersionHandler.java:133)
at org.fcrepo.migration.handlers.VersionAbstractionFedoraObjectHandler.processObject(VersionAbstractionFedoraObjectHandler.java:95)
at org.fcrepo.migration.handlers.ObjectAbstractionStreamingFedoraObjectHandler.completeObject(ObjectAbstractionStreamingFedoraObjectHandler.java:67)
at org.fcrepo.migration.foxml11.Foxml11InputStreamFedoraObjectProcessor.processObject(Foxml11InputStreamFedoraObjectProcessor.java:124)
at org.fcrepo.migration.Migrator.run(Migrator.java:101)
at org.fcrepo.migration.Migrator.main(Migrator.java:37)

Could you copy the line 439 of your BsaicObjectVersionHandler @bcail so I can figure out what's null?

439 updateResourceProperties(ds, triplesToRemove, triplesToInsert);

@bcail I'm sorry I can't seem to figure out what's wrong. I'm not sure how that line could result in a NPE, since no objects are dereferenced.

@mikedurbin maybe ds is null? In any case, though, there's a unit test - maybe the PR should just be merged. I can try again with the latest master after it's merged...

@mikedurbin, do we merge this?

It's possible (likely) there's an outstanding bug that results in the NullPointerException, whether it was introduced by this commit or not is unclear. I'm pretty sure this PR addresses the issue described in the ticket.

So yeah... if you're asking me... let's merge it and move on to the next issue people run across.