Merge pull request #9 from tddbc/dependabot/pip/virtualenv-20.26.6

Bump virtualenv from 20.4.6 to 20.26.6

Author: hiro-iseri

requirements.txt

@@ -11,4 +11,4 @@ pytest-cov==2.11.1
 pytest-xdist==2.2.1
 pytest==6.2.4
 tox==3.23.1
-virtualenv==20.4.6
+virtualenv==20.26.6