Those lines were whitespace reformed by Antoine in 61466/61463.
They previously came from 28325 which fixed #663074 (2003).
I do not see any discussion in that issue of making the import optional.
I suspect there is no test of Python working with no encodings ;-)

Just for fun, I commented out the import and error checks. There is an error message during the build about python_d.exe not working and python_d.exe crashes (ungracefully) on explicit startup, as you expected. I presume the patch is to delete the entire block added in 28325:
        if (PyErr_ExceptionMatches(PyExc_ImportError)) {
            /* Ignore ImportErrors... this is done so that
               distributions can disable the encodings package. Note
               that other errors are not masked, e.g. SystemErrors
               raised to inform the user of an error in the Python
               configuration are still reported back to the user. */
            PyErr_Clear();
            return 0;

Only in 3.3 or further back? I can do it if you like.