Last set of change to get regression tests to pass

Last set of change to get regression tests to pass

Remove the only test in the syntax module.  It ends up that the
transformer must handle this error case.

In the transformer, check for a list compression in com_assign_list()
by looking for a list_for node where a comma is expected.

In pycodegen.compile() re-raise the SyntaxError rather than catching
it and exiting