          field = self.field
          for input_value in inputs:
              with pytest.raises(serializers.ValidationError) as exc_info:
                  field.run_validation(input_value)
              expected = ['Must be a valid boolean.'.format(input_value)]
              assert exc_info.value.detail == expected
  
  
  class TestNullBooleanField(TestBooleanField):
      """
 
</s> remove             'lang_htmls': ["rest_framework/docs/langs/%s.html" % l for l in self.languages],
            'lang_intro_htmls': ["rest_framework/docs/langs/%s-intro.html" % l for l in self.languages],
 </s> add             'lang_htmls': ["rest_framework/docs/langs/%s.html" % language for language in self.languages],
            'lang_intro_htmls': ["rest_framework/docs/langs/%s-intro.html" % language for language in self.languages], </s> remove         'app_label': model._meta.app_label,
 </s> add  </s> remove pycodestyle==2.5.0
 </s> add pycodestyle==2.6.0 </s> remove flake8==3.7.9
 </s> add flake8==3.8.3
            expected = ['Must be a valid boolean.']
          field = self.field
          for input_value in inputs:
              with pytest.raises(serializers.ValidationError) as exc_info:
                  field.run_validation(input_value)
            expected = ['Must be a valid boolean.']
              assert exc_info.value.detail == expected
  
  
  class TestNullBooleanField(TestBooleanField):
      """
keep keep keep keep replace keep keep keep keep keep
 Bump flake8 to 3.8.3 (#7521) 
tests/test_fields.py