I looked and the file exists:
$ file Python/Python-ast.c
Python/Python-ast.c: C source, ASCII text

The file appears valid.

I touched the files as suggested but I still I get the same error message when running "configure".

FWIW, the Makefile.pre.in target exists but it doesn't seem useful because this happens just by running configure (when there is no Makefile).
I should note that I am attempting to build within FreeBSD's ports tree (apparently out-of-tree) so maybe my environment setup is causing the trouble.