code: def get_env_value(obj, attribute):
      
      varname = get_env_key(obj, attribute)
      var = os.environ.get(varname)
      if not var:
          raise ValueError("%s must be set in your environment." % varname)
  
      return var
docs: Returns the environment variable value for the attribute of
      the given object.
  
      For example `get_env_value(predix.security.uaa, 'uri')` will
      return value of environment variable PREDIX_SECURITY_UAA_URI.