-pip install --quiet --upgrade pip
-pip install --quiet --upgrade pipdeptree
-pip install --quiet --upgrade "lftools<1.0.0"
+PYTHON="$WORKSPACE/.virtualenvs/lftools/bin/python"
+$PYTHON -m pip install --quiet --upgrade pip
+$PYTHON -m pip install --quiet --upgrade pipdeptree
+$PYTHON -m pip install --quiet --upgrade "lftools<1.0.0"