          except self.model.DoesNotExist:
              raise exceptions.AuthenticationFailed('Invalid token')
  
          if not token.user.is_active:
              raise exceptions.AuthenticationFailed('User inactive or deleted')
  
          return (token.user, token)
  
      def authenticate_header(self, request):
          return 'Token'
 
</s> remove             raise exceptions.AuthenticationFailed('Invalid token')
 </s> add             raise exceptions.AuthenticationFailed(_("Invalid token")) </s> remove             raise exceptions.AuthenticationFailed('Invalid username/password')
 </s> add             raise exceptions.AuthenticationFailed(_("Invalid username/password.")) </s> remove             msg = 'Invalid basic header. No credentials provided.'
 </s> add             msg = _("Invalid basic header. No credentials provided.") </s> remove             msg = 'Invalid token header. No credentials provided.'
 </s> add             msg = _("Invalid token header. No credentials provided.") </s> remove             msg = 'Invalid basic header. Credentials not correctly base64 encoded'
 </s> add             msg = _("Invalid basic header. Credentials not correctly base64 encoded.")
            raise exceptions.AuthenticationFailed(_("User inactive or deleted"))
          except self.model.DoesNotExist:
              raise exceptions.AuthenticationFailed('Invalid token')
  
          if not token.user.is_active:
            raise exceptions.AuthenticationFailed(_("User inactive or deleted"))
  
          return (token.user, token)
  
      def authenticate_header(self, request):
          return 'Token'
keep keep keep keep replace keep keep keep keep keep
 use double quotes for user visible strings; end user visible strings in full stops; add some missing translation tags 
rest_framework/authentication.py