Add support for Python 3.6 (thanks sose)

update_linux.sh

@@ -11,7 +11,7 @@ fi
 if ! command -v virtualenv &> /dev/null
 then
 	echo "virtualenv could not be found, please install with:"
-	echo "sudo apt install python3-virtualenv"
+	echo "sudo apt install virtualenv"
 	exit
 fi
 
@@ -71,6 +71,9 @@ git pull --rebase
 git stash pop || true
 
 
+# https://github.com/pypa/virtualenv/issues/1029
+PS1=${PS1:-}
+
 # create virtual environment
 
 echo "Installing Python requirements..."