Improve error on python syntax error

The attached pipeline has some bad python syntax. When you try deploying the pipeline, all that comes back is an unhelpful error message that says:

Error configuring stage 'Python': null

I've attached a screenshot of the error.

The root cause is a bad exception thrown by jython:

But the plugin should at least be catching the PySyntaxError and telling the user that there is a syntax error, though what the error is can't be determined if jython isn't saying what it is.