This code:

from enum import Enum

class Responses(str, Enum):
    NORMAL = 'something'
    TEMPLATED = 'insert {value} here'

Responses.TEMPLATED.format(value=42)

fails with Not all arguments converted during string formatting. Using this as Responses.TEMPLATED.value.format(value=42) fixes the issue. Both ways actually work with string enums at runtime (only the latter works with normal enums).