requirements-dev: Update pytest-virtualenv from 1.2.2 to 1.2.4

Author: jcfr

requirements-dev.txt

@@ -4,7 +4,6 @@ flake8==3.0.4
 pytest==3.0.3
 pytest-cov==2.4.0
 pytest-runner==2.9
-git+https://github.com/jcfr/pytest-plugins@pytest-shutil-2016-11-08-c50ac56#egg=pytest-shutil
-pytest-virtualenv==1.2.2
+pytest-virtualenv==1.2.4
 scikit-build==0.4.0
 virtualenv==15.0.3