Update makefile

Makefile

@@ -4,8 +4,8 @@ MARKER=.initialized-with-makefile
 VENVDEPS=$(REQUIREMENTS setup.py)
 
 $(VENV):
-	python -m venv .venv
-	$(VENV)/python -m pip install --upgrade pip setuptools wheel
+	python3 -m venv .venv
+	$(VENV)/python3 -m pip install --upgrade pip setuptools wheel
 
 $(VENV)/$(MARKER): $(VENVDEPS) | $(VENV)
 	$(VENV)/pip install $(foreach path,$(REQUIREMENTS),-r $(path))
@@ -19,13 +19,13 @@ lint: venv
 	$(VENV)/pylint percy/* tests/*
 
 test: venv
-	$(VENV)/python -m unittest discover
+	$(VENV)/python3 -m unittest discover
 
 clean:
 	rm -rf $$(cat .gitignore)
 
 build: venv
-	$(VENV)/python setup.py sdist bdist_wheel
+	$(VENV)/python3 setup.py sdist bdist_wheel
 
 release: build
 	$(VENV)/twine upload dist/* --username __token__ --password ${PYPI_TOKEN}