Rebuild virtualenv on requirements change.

.gitignore

@@ -8,6 +8,7 @@
 .project
 .pydevproject
 .tox
+.venv.touch
 /venv*
 coverage-html
 dist

Makefile

@@ -1,17 +1,27 @@
+
+REBUILD_FLAG =
+
 .PHONY: all
 all: venv test
 
 .PHONY: venv
-venv:
-	tox -e venv
+venv: .venv.touch
+	tox -e venv $(REBUILD_FLAG)
 
 .PHONY: tests test
 tests: test
-test:
-	tox
+test: .venv.touch
+	tox $(REBUILD_FLAG)
+
+
+.venv.touch: setup.py requirements.txt requirements_dev.txt
+	$(eval REBUILD_FLAG := --recreate)
+	touch .venv.touch
+
 
 .PHONY: clean
 clean:
 	find . -iname '*.pyc' | xargs rm -f
 	rm -rf .tox
 	rm -rf ./venv-*
+	rm -f .venv.touch