Adding check for node key in Context
Adding check for node key in Context

This change adds a check for the existence of the 'node' key in the
Context._context

Change-Id: Ic5184bb39352c4ec003fe36ad7bd98751dd7d7da
Closes-Bug: 1491130

pombredanne/bandit,pombredanne/bandit,stackforge/bandit,stackforge/bandit,chair6/bandit