def pip_install(self, reqs):
        """Install dependencies into this env by calling pip in a subprocess"""
        if not reqs:
            return
        log.info('Calling pip to install %s', reqs)
        check_call([
            sys.executable, '-m', 'pip', 'install', '--ignore-installed',
            '--prefix', self.path] + list(reqs))
Install dependencies into this env by calling pip in a subprocess
stackoverflow/venv/lib/python3.6/site-packages/pip-19.0.3-py3.6.egg/pip/_vendor/pep517/envbuild.py