Minor Description
I'm not sure there's much that can be done in general cases during traversal construction as the error will occur in the application building the traversal but for the Console and Server we can better capture that error condition and provide a better error message with advice on how resolve it.
To implement this in the Gremlin Console, on the 3.4.x release series, we need this PR to merge and a fresh release of groovy on their 2.5.x line: