                  field_name, info, model, depth
              )
  
              # Include any kwargs defined in `Meta.extra_kwargs`
              extra_field_kwargs = extra_kwargs.get(field_name, {})
              field_kwargs = self.include_extra_kwargs(
                  field_kwargs, extra_field_kwargs
              )
  
              # Create the serializer field.
 
</s> remove                 field_name, info, model, depth
 </s> add                 source, info, model, depth
                  field_name, info, model, depth
              )
  
              # Include any kwargs defined in `Meta.extra_kwargs`

              field_kwargs = self.include_extra_kwargs(
                  field_kwargs, extra_field_kwargs
              )
  
              # Create the serializer field.
keep keep keep keep replace keep keep keep keep keep
 Do not ignore source when building fields dynamically

This commit fixes the issue when you set the keyword argument `source`
and your have not set the serializer fields explicitly. Then the
construction of field failed because there is not actually any model
field with that name.

However, you are still able to imply the name of model field by
providing the `source` keyword argument. 
rest_framework/serializers.py