use format_lazy instead of format for lazy objects

[HosseinMohammadii]

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Due to django docs for lazy objects format_lazy method should be called instead of str.format.
https://docs.djangoproject.com/en/3.1/topics/i18n/translation/#formatting-strings-format-lazy

because in serializers instead of lazy objects, str objects are passed to Exception initiation, I can't access lazy objects in exception handler.
for example in this part that it seems a little wrong

django-rest-framework/rest_framework/validators.py

Line 159 in 8351747

message = self.message.format(field_names=field_names)

Thanks