Code review comment for lp://staging/~nejucomo/divmod.org/fix-nevow-setup

I am dusting this off again, in order to write unittests for the setup.py changes.

Before I begin changing tests, I ran `trial nevow` in the source root directory *without a nevow* install, and see the following error:

{{{
nevow.test.test_url.Serialization.test_rfc1808
===============================================================================
[ERROR]
Traceback (most recent call last):
Failure: twisted.internet.utils._UnexpectedErrorOutput: got stderr: 'Could not create the Java virtual machine.\n'
}}}