Use built-in venv module to create virtualenv

Makefile

@@ -28,7 +28,7 @@ install-js: ## Install js requirements
 	npm install
 
 venv: ## Create a virtual env and install test and production requirements
-	virtualenv --python=$(shell which python3) $(VENV)
+	$(shell which python3) -m venv $(VENV)
 	$(VENV)/bin/pip install -e .[test]
 	$(VENV)/bin/pip install -r docs/requirements.txt
 

docs/source/internals/contributing/running-tests.rst

@@ -25,11 +25,10 @@ This will create a virtualenv in `venv`, install the test dependencies and run p
 Details
 ~~~~~~~
 
-First we create a virtualenv and install the required dependencies::
+First we create a virtualenv, install the required dependencies and activate it::
 
-    $ virtualenv venv
+    $ make venv
     $ source venv/bin/activate
-    $ pip install -e .[test]
 
 Then we invoke pytest using ::