scripts:bootstrap: only source .env file if it exists

Also fix shellcheck warning when sourced files do not exist

scripts/bootstrap.sh

@@ -6,20 +6,26 @@ set -e #ux
 cwd="$(pwd)"
 ## Change to project directory
 cd "$(dirname "$0")/.."
-# shellcheck source="../.env"
-source .env
+if [ -f .env ]; then
+  # shellcheck source="../.env" disable=SC1091
+  source .env
+fi
 
 ./scripts/python_setup.sh "$@"
 
 echo "-- Shell: Source profile in case it's been updated"
-# shellcheck source="$HOME/.profile"
+# shellcheck source="$HOME/.profile" disable=SC1091
 source "$HOME/.profile"
+
 echo "-- Activate Python virtual environment"
 # shellcheck source="../.venv/bin/activate"
 source .venv/bin/activate
-echo "-- Source '.env' configuration file"
-# shellcheck source="../.env"
-source .env
+
+if [ -f .env ]; then
+  echo "-- Source '.env' configuration file"
+  # shellcheck source="../.env" disable=SC1091
+  source .env
+fi
 
 ## and go back
 cd "$cwd"