import os
import sys

def validate_env_vars(required_vars):
    """
    Checks that all required environment variables are set. Exits with an error if any are missing.
    """
    missing = [var for var in required_vars if not os.getenv(var)]
    if missing:
        sys.stderr.write(f"Missing required environment variables: {', '.join(missing)}\n")
        sys.exit(1)