Deserialisation errors seen with class hudson.EnvVars:

 java.io.InvalidClassException: hudson.EnvVars; local class incompatible: stream classdesc serialVersionUID = -234198271843838088, local class serialVersionUID = 4320331661987259022

hudson.EnvVars is serialisable, but doesn't have a serialVersionUID. The generated one has changed between v2.138 (-234198271843838088) & v2.150 (4320331661987259022) causing these deserialisation errors.

This is to ensure the compatibility with a derived tool and as it's good practise to have a static serialVersionUID, we should add it.