code: def set_env_value(obj, attribute, value):
      
      varname = get_env_key(obj, attribute)
      os.environ[varname] = value
      return varname
docs: Set the environment variable value for the attribute of the
      given object.
  
      For example, `set_env_value(predix.security.uaa, 'uri', 'http://...')`
      will set the environment variable PREDIX_SECURITY_UAA_URI to the given
      uri.