javax/xml/crypto/dsig/LogParameters.java failed with "RuntimeException: Unexpected log output:"

The following test failed in the JDK16 CI:

javax/xml/crypto/dsig/LogParameters.java

Here's a snippet from the log file:

#section:main
----------messages:(6/248)----------
command: main LogParameters
reason: Assumed action based on file name: run main LogParameters
Mode: agentvm
Agent id: 10
Additional exports to unnamed modules from @modules: java.xml.crypto/com.sun.org.slf4j.internal
elapsed time (seconds): 0.026
----------configuration:(14/1668)----------
Boot Layer
  class path: /scratch/mesos/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/javatest.jar
              /scratch/mesos/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/jtreg.jar
              /scratch/mesos/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/junit.jar
              /scratch/mesos/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/testng.jar
  patch: java.base /scratch/mesos/slaves/4076d11c-c6ed-4d07-84c1-4ab8d55cd975-S149434/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/7fe6ad87-a783-499e-9b46-390bd822ab3d/runs/d04915fe-186c-43cd-9844-06579e4a71e9/testoutput/test-support/jtreg_open_test_jdk_tier2_part1/patches/java.base

Test Layer
  add exports: java.xml.crypto/com.sun.org.slf4j.internal ALL-UNNAMED
  class path: /scratch/mesos/slaves/4076d11c-c6ed-4d07-84c1-4ab8d55cd975-S149434/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/7fe6ad87-a783-499e-9b46-390bd822ab3d/runs/d04915fe-186c-43cd-9844-06579e4a71e9/testoutput/test-support/jtreg_open_test_jdk_tier2_part1/classes/1/javax/xml/crypto/dsig/LogParameters.d
               /scratch/mesos/jib-master/install/jdk-16+20-1009/src.full/open/test/jdk/javax/xml/crypto/dsig
               /scratch/mesos/slaves/4076d11c-c6ed-4d07-84c1-4ab8d55cd975-S149434/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/7fe6ad87-a783-499e-9b46-390bd822ab3d/runs/d04915fe-186c-43cd-9844-06579e4a71e9/testoutput/test-support/jtreg_open_test_jdk_tier2_part1/classes/1/test/lib
               /scratch/mesos/jib-master/install/jdk-16+20-1009/src.full/open/test/lib

----------rerun:(31/5640)*----------
<snip>

----------System.err:(12/711)----------
java.lang.RuntimeException: Unexpected log output:
at LogParameters.main(LogParameters.java:55)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:298)
at java.base/java.lang.Thread.run(Thread.java:832)

JavaTest Message: Test threw exception: java.lang.RuntimeException
JavaTest Message: shutting down test

result: Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: Unexpected log output:


test result: Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: Unexpected log output:


It is not at all clear what the unexpected log output is.