code: def env(var_name, default=False):
      
      try:
          value = os.environ[var_name]
          if str(value).strip().lower() in ['false', 'f', 'no', 'off' '0', 'none', 'null', '', ]:
              return None
          return value
      except:
          from traceback import format_exc
          msg = "Unable to find the %s environment variable.\nUsing the value %s (the default) instead.\n" % (var_name, default)
          sys.stderr.write(format_exc())
          sys.stderr.write(msg)
          return default
docs: Get the environment variable. If not found use a default or False, but print to stderr a warning about the missing env variable.