install: Remove the hidden VIRTUALENV_NEEDED parameter.

We can do this behaviour better by using `has_roles`.

scripts/lib/install

@@ -151,7 +151,6 @@ read -r -a ADDITIONAL_PACKAGES <<<"${ADDITIONAL_PACKAGES:-}"
 # zulip::profile::docker for Docker.  Use
 # e.g. zulip::profile::app_frontend for a Zulip frontend server.
 PUPPET_CLASSES="${PUPPET_CLASSES:-zulip::profile::standalone}"
-VIRTUALENV_NEEDED="${VIRTUALENV_NEEDED:-yes}"
 POSTGRESQL_VERSION="${POSTGRESQL_VERSION:-16}"
 
 if [ -n "$SELF_SIGNED_CERT" ] && [ -n "$USE_CERTBOT" ]; then
@@ -398,11 +397,6 @@ if [ -n "$SELF_SIGNED_CERT" ] || [ -n "$USE_CERTBOT" ]; then
         --exists-ok "${EXTERNAL_HOST:-$(hostname)}"
 fi
 
-# Create and activate a virtualenv
-if [ "$VIRTUALENV_NEEDED" = "yes" ]; then
-    "$ZULIP_PATH"/scripts/lib/create-production-venv "$ZULIP_PATH"
-fi
-
 # Generate /etc/zulip/zulip.conf .
 mkdir -p /etc/zulip
 has_class() {
@@ -454,6 +448,9 @@ EOF
 fi
 
 if has_class "zulip::app_frontend_base"; then
+    # Create and activate a virtualenv
+    "$ZULIP_PATH"/scripts/lib/create-production-venv "$ZULIP_PATH"
+
     "$ZULIP_PATH"/scripts/lib/install-node
 
     if [ -z "$NO_OVERWRITE_SETTINGS" ] || ! [ -e "/etc/zulip/settings.py" ]; then

tools/setup/bootstrap-aws-installer

@@ -71,8 +71,6 @@ git clone "$REPO_URL" zulip -b "$BRANCH"
 git -C zulip checkout "$BRANCH"
 
 (
-    VIRTUALENV_NEEDED=$(if echo "$FULL_ROLES" | grep -q app_frontend; then echo -n yes; else echo -n no; fi)
-    export VIRTUALENV_NEEDED
     export PUPPET_CLASSES="$FULL_ROLES"
     export APT_OPTIONS="-o Dpkg::Options::=--force-confnew"
     /root/zulip/scripts/setup/install \