updated calls to Path.resolve() in Writable.write to be python 3.5+ compatible
updated calls to Path.resolve() in Writable.write to be python 3.5+ compatible

pegasus-isi/pegasus,pegasus-isi/pegasus,pegasus-isi/pegasus,pegasus-isi/pegasus,pegasus-isi/pegasus,pegasus-isi/pegasus,pegasus-isi/pegasus,pegasus-isi/pegasus,pegasus-isi/pegasus,pegasus-isi/pegasus