Change use of python in ParaView to be Python3 compatible.
The most common changes:
print "foo" => print ("foo")
raise RuntimeError, "failed" => raise RuntimeError("failed")
next() => __next__()
import of relative submodules is disallowed.
use import __future__ to get python3 behavior in python2

Spot fixes:
map() returns an iterable, not a list
type str now has attr __iter__, so looks iterable.