JENKINS-52390 Throw appropriate error when the code is not in node block

[nrayapati]

Description

• Update examples to surround code with node.
• Throw appropriate error when the code is not in node block.

See JENKINS-52390.

[nrayapati]

Instead of throwing java.lang.NullPointerException, it would now throw a valid error message

Before: 👎

[Pipeline] stage
[Pipeline] { (Remote SSH)
[Pipeline] sshCommand
[Pipeline] }
[Pipeline] // stage
[Pipeline] End of Pipeline
[Office365connector] No webhooks to notify
java.lang.NullPointerException
	at org.jenkinsci.plugins.sshsteps.steps.CommandStep$Execution.run(CommandStep.java:71)
	at org.jenkinsci.plugins.sshsteps.util.SSHStepExecution$1$1.call(SSHStepExecution.java:77)
	at hudson.security.ACL.impersonate(ACL.java:290)
	at org.jenkinsci.plugins.sshsteps.util.SSHStepExecution$1.run(SSHStepExecution.java:72)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Finished: FAILURE

After: 👍

[Pipeline] stage
[Pipeline] { (Remote SSH)
[Pipeline] sshCommand
Required context class hudson.Launcher is missing
Perhaps you forgot to surround the code with a step that provides this, such as: node
[Pipeline] }
[Pipeline] // stage
[Pipeline] End of Pipeline
[Office365connector] No webhooks to notify
org.jenkinsci.plugins.workflow.steps.MissingContextVariableException: Required context class hudson.Launcher is missing
	at org.jenkinsci.plugins.workflow.steps.StepDescriptor.checkContextAvailability(StepDescriptor.java:260)
	at org.jenkinsci.plugins.workflow.cps.DSL.invokeStep(DSL.java:206)
	at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:153)

[nrayapati]

Thank you @wuchenwang

[nrayapati]

Thank you @ghenkes