Trying to diagnose a random failure in DSLTest.overrideFunction.
java.lang.NullPointerException
 at org.jenkinsci.plugins.workflow.cps.CpsStepContext.getThreadSynchronously(CpsStepContext.java:211)
 at org.jenkinsci.plugins.workflow.cps.CpsStepContext.doGet(CpsStepContext.java:272)
 at org.jenkinsci.plugins.workflow.support.DefaultStepContext.get(DefaultStepContext.java:64)
 at org.jenkinsci.plugins.workflow.steps.StepDescriptor.checkContextAvailability(StepDescriptor.java:115)
 at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:132)