Use venv rather than virtualenv (#357)

Summary:
Use venv rather than virtualenv

venv has been included as part of the python standard library since 3.3 -- no need to install the third-party virtualenv module

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[//]: # (BEGIN SAPLING FOOTER)
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* #359
* __->__ #357

Pull Request resolved: #357

Differential Revision: D55365458

Pulled By: shish

fbshipit-source-id: 0312bd52e37ba4d78572dcd2d616578dd820a92f

.github/workflows/build.yml

@@ -18,8 +18,6 @@ jobs:
       uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
-    - name: Install virtualenv
-      run: pip install virtualenv
     - name: Run Tests
       run: TESTSLIDE_FORMAT=progress UNITTEST_VERBOSE=0 make ci V=1
     - name: Coveralls

Makefile

@@ -42,7 +42,7 @@ all: tests coverage_report docs sdist
 ##
 venv: requirements-dev.txt requirements.txt
 	@printf "${TERM_BRIGHT}CREATE VIRTUALENV (${CURDIR}/venv)\n${TERM_NONE}"
-	${Q} python3 -m virtualenv venv
+	${Q} python3 -m venv venv
 	@printf "${TERM_BRIGHT}INSTALL BUILD DEPS\n${TERM_NONE}"
 	${Q} ${CURDIR}/venv/bin/pip install -r requirements-dev.txt
 	@printf "${TERM_BRIGHT}INSTALL DEPS\n${TERM_NONE}"