Force virtualenv version

Force the virtualenv version to be 20.11 or less.
The 20.12 version is failing for python 2 right now.

python-setup/install_tools.ps1

@@ -5,9 +5,9 @@ py -3 -m pip install --user --upgrade pip setuptools wheel
 
 # virtualenv is a bit nicer for setting up virtual environment, since it will provide up-to-date versions of
 # pip/setuptools/wheel which basic `python3 -m venv venv` won't
-py -2 -m pip install --user virtualenv
-py -3 -m pip install --user virtualenv
+py -2 -m pip install --user 'virtualenv<20.11'
+py -3 -m pip install --user 'virtualenv<20.11'
 
 # poetry 1.0.10 has error (https://github.com/python-poetry/poetry/issues/2711)
 py -3 -m pip install --user poetry!=1.0.10
-py -3 -m pip install --user pipenv
+py -3 -m pip install --user pipenv

python-setup/install_tools.sh

@@ -15,7 +15,7 @@ python3 -m pip install --user --upgrade pip setuptools wheel
 
 # virtualenv is a bit nicer for setting up virtual environment, since it will provide up-to-date versions of
 # pip/setuptools/wheel which basic `python3 -m venv venv` won't
-python3 -m pip install --user virtualenv
+python3 -m pip install --user 'virtualenv<20.11'
 
 # We install poetry with pip instead of the recommended way, since the recommended way
 # caused some problem since `poetry run` gives output like:
@@ -35,5 +35,5 @@ if command -v python2 &> /dev/null; then
 
 	python2 -m pip install --user --upgrade pip setuptools wheel
 
-	python2 -m pip install --user virtualenv
+	python2 -m pip install --user 'virtualenv<20.11'
 fi