update to python 3..

ui/Makefile

@@ -1,16 +1,17 @@
+VIRTUALENV?=virtualenv-3.7
 MODULES=cli.py kleintest.py mtree.py server.py
 
 test: fixtures/sample.data.pasn1 fixtures/sample.persona.pasn1 fixtures/sample.mtree
 	(. ./p/bin/activate && \
-		(ls $(MODULES) | entr sh -c 'python -m coverage run -m unittest $(basename $(MODULES)) && coverage report -m --omit=p/\*'))
+		(ls $(MODULES) | entr sh -c 'python3 -m coverage run -m unittest -f $(basename $(MODULES)) && coverage report -m --omit=p/\*'))
 
 env:
-	virtualenv p
+	$(VIRTUALENV) p
 	(. ./p/bin/activate && \
 		pip install -r requirements.txt)
 
 fixtures/sample.data.pasn1 fixtures/sample.persona.pasn1: fixtures/genfixtures.py
-	(. ./p/bin/activate && cd fixtures && PYTHONPATH=.. python genfixtures.py )
+	(. ./p/bin/activate && cd fixtures && PYTHONPATH=.. python3 genfixtures.py )
 
 fixtures/sample.mtree: fixtures/mtree.dir
 	bsdtar -cf - --format mtree --options='!all,time,sha512,size,indent' -C fixtures/mtree.dir . > $@