For JTREG tests, when collecting code coverage with JCov (JDK-8215729), tests run with env:
JAVA_TOOL_OPTIONS=<options>
_JAVA_OPTIONS=<options>

And it prints:

Picked up JAVA_TOOL_OPTIONS: <options>
Picked up _JAVA_OPTIONS: <options>

to stderr.

Test that expects stderr either to be empty or it must match the given patterns then fail due to extra unexpected message (above) in stderr.

Please note that it's NOT possible to suppress the message of Picked up _JAVA_OPTIONS and JAVA_TOOL_OPTIONS, see JDK-8039152

To make test "pass", we have to tolerate these warnings in test. It's better enhancement can be done to
jdk.test.lib.process.OutputAnalyzer

either by improving
OutputAnalyzer::stderrShouldBeEmptyIgnoreVMWarnings
and/or introduce similar method to take care the mentioned message.