There appear to be some missing translations in djangorestframework 3.10.3.

I tried to sign up for transifex to fix the issue directly, and to definitely confirm that it is a missing translation and not an issue on my end, but I was unable to do so.

Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

• Set Django LANGUAGE_CODE to ja
  • Alternatively use django.utils.translation.activate('ja')
• Create a Serializer with a Boolean field
• Pass an invalid value to the boolean field

Expected behavior

The validation error will be in Japanese.

Actual behavior

The validation error is in English, Must be a valid boolean.

Note: Other error messages are in Japanese, such as an error for None values in Required fields.

• If you put '2' in to the field, you get "Must be a valid boolean.".
• If you don't put anything in to the field, you get 'この項目は必須です。'