Where is the "from future import braces" code?

I was wondering what is exactly the code that executed on the command:

    >>> from __future__ import braces
    SyntaxError: not a chance

so, since python is open-sourced I opened C:\Python27\Lib\__future__.py and looked. surprisingly, I found nothing there that handle importing braces module.

so, my question is, where is the code that handle this? what happen when I run that command?

The code is in future.c:

    future_check_features(PyFutureFeatures *ff, stmt_ty s, const char *filename)
    ...
      else if (strcmp(feature, "braces") == 0) {
        PyErr_SetString(PyExc_SyntaxError,
            "not a chance");
        PyErr_SyntaxLocation(filename, s->lineno);
        return 0;
      }

From: stackoverflow.com/q/21125228