Test failure on Windows, perhaps specific to filesystem type of TemporaryFolder.

java.nio.file.FileSystemException: …\.ssh\known_hosts: Incorrect function.
        at sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:86)
        at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:90)
        at sun.nio.fs.WindowsAclFileAttributeView.getFileSecurity(WindowsAclFileAttributeView.java:88)
        at sun.nio.fs.WindowsAclFileAttributeView.getOwner(WindowsAclFileAttributeView.java:121)
        at sun.nio.fs.FileOwnerAttributeViewImpl.getOwner(FileOwnerAttributeViewImpl.java:91)
        at java.nio.file.Files.getOwner(Files.java:2079)
        at org.apache.sshd.common.util.io.IoUtils.getFileOwner(IoUtils.java:272)
        at org.apache.sshd.common.util.io.ModifiableFileWatcher.validateStrictConfigFilePermissions(ModifiableFileWatcher.java:240)
        at org.apache.sshd.client.keyverifier.DefaultKnownHostsServerKeyVerifier.reloadKnownHosts(DefaultKnownHostsServerKeyVerifier.java:79)
        at org.apache.sshd.client.keyverifier.KnownHostsServerKeyVerifier.verifyServerKey(KnownHostsServerKeyVerifier.java:161)
        at …
Interactive testing of known_hosts on XP works as expected.

cli/src/main/java/hudson/cli/CLI.java

@@ -541,7 +541,7 @@ public class CLI implements AutoCloseable {
                 Level level = parse(args.get(1));
                 ConsoleHandler h = new ConsoleHandler();
                 h.setLevel(level);
-                for (Logger logger : new Logger[] {LOGGER, PlainCLIProtocol.LOGGER}) { // perhaps also Channel
+                for (Logger logger : new Logger[] {LOGGER, PlainCLIProtocol.LOGGER, Logger.getLogger("org.apache.sshd")}) { // perhaps also Channel
                     logger.setLevel(level);
                     logger.addHandler(h);
                 }

test/src/test/java/hudson/cli/CLITest.java

@@ -29,6 +29,8 @@ import hudson.model.User;
 import hudson.util.StreamTaskListener;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
 import jenkins.model.Jenkins;
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.IOUtils;
@@ -36,6 +38,7 @@ import static org.hamcrest.Matchers.containsString;
 import org.jenkinsci.main.modules.cli.auth.ssh.UserPropertyImpl;
 import org.jenkinsci.main.modules.sshd.SSHD;
 import static org.junit.Assert.*;
+import static org.junit.Assume.*;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
@@ -57,10 +60,15 @@ public class CLITest {
         File home = tmp.newFolder();
         // Seems it gets created automatically but with inappropriate permissions:
         File known_hosts = new File(new File(home, ".ssh"), "known_hosts");
-        assertTrue(known_hosts.getParentFile().mkdir());
-        assertTrue(known_hosts.createNewFile());
-        assertTrue(known_hosts.setWritable(false, false));
-        assertTrue(known_hosts.setWritable(true, true));
+        assumeTrue(known_hosts.getParentFile().mkdir());
+        assumeTrue(known_hosts.createNewFile());
+        assumeTrue(known_hosts.setWritable(false, false));
+        assumeTrue(known_hosts.setWritable(true, true));
+        try {
+            Files.getOwner(known_hosts.toPath());
+        } catch (IOException x) {
+            assumeNoException("Sometimes on Windows KnownHostsServerKeyVerifier.acceptIncompleteHostKeys says WARNING: Failed (FileSystemException) to reload server keys from …\\\\.ssh\\\\known_hosts: … Incorrect function.", x);
+        }
         r.jenkins.setSecurityRealm(r.createDummySecurityRealm());
         r.jenkins.setAuthorizationStrategy(new MockAuthorizationStrategy().grant(Jenkins.ADMINISTER).everywhere().to("admin"));
         SSHD.get().setPort(0);
@@ -74,7 +82,7 @@ public class CLITest {
         ).stdout(System.out).stderr(System.err).join());
         ByteArrayOutputStream baos = new ByteArrayOutputStream();
         assertEquals(0, new Launcher.LocalLauncher(StreamTaskListener.fromStderr()).launch().cmds(
-            "java", "-Duser.home=" + home, "-jar", jar.getAbsolutePath(), "-s", r.getURL().toString(), "-ssh", "-user", "admin", "-i", privkey.getAbsolutePath(), "who-am-i"
+            "java", "-Duser.home=" + home, "-jar", jar.getAbsolutePath(), "-s", r.getURL().toString(), "-ssh", "-user", "admin", "-i", privkey.getAbsolutePath(), "-logger", "FINEST",  "who-am-i"
         ).stdout(baos).stderr(System.err).join());
         assertThat(baos.toString(), containsString("Authenticated as: admin"));
         baos = new ByteArrayOutputStream();