feat: show error message when pipeline syntax is wrong

[ankitm123]

Signed-off-by: ankitm123 ankitmohapatra123@gmail.com

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[nicolaerosia]

This would be helpful!

[jenkins-x-bot]

@ankitm123: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
pr	ba60b04	link	/test

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