python: poetry: unset VIRTUAL_ENV

This is needed as tools like poetry looks for VIRTUAL_ENV and attempts
to use the python interpreter from this environment.

We want poetry to use the python interpreter from PATH (set by devenv).
We want it to configure the python interpreter for the new venv.

src/modules/languages/python.nix

@@ -6,6 +6,10 @@ let
   venvPath = "${config.env.DEVENV_STATE}/venv";
 
   initVenvScript = pkgs.writeShellScript "init-venv.sh" ''
+    # Make sure any tools are not attempting to use the python interpreter from any
+    # existing virtual environment. For instance if devenv was started within an venv.
+    unset VIRTUAL_ENV
+
     if [ ! -L ${venvPath}/devenv-profile ] \
     || [ "$(${pkgs.coreutils}/bin/readlink ${venvPath}/devenv-profile)" != "${config.env.DEVENV_PROFILE}" ]
     then
@@ -26,6 +30,10 @@ let
   initPoetryScript = pkgs.writeShellScript "init-poetry.sh" ''
     function _devenv-init-poetry-venv()
     {
+      # Make sure any tools are not attempting to use the python interpreter from any
+      # existing virtual environment. For instance if devenv was started within an venv.
+      unset VIRTUAL_ENV
+
       if [ ! -L ${config.env.DEVENV_ROOT}/.venv ]
       then
         ${pkgs.coreutils}/bin/ln --symbolic --no-target-directory --force ${venvPath} ${config.env.DEVENV_ROOT}/.venv