Confirmed in trunk and py3k. Changing to RFE, set it to behavior if you
disagree.

Python 2.4 does return "" for str.replace("", "", "asdf", -1), the
change happened in rev46226, with the effbot adding this snippet (by
Andrew Dalke?):

      if (maxcount < 0) {
             maxcount = PY_SSIZE_T_MAX;
      } else if (maxcount == 0 || PyString_GET_SIZE(self) == 0) {
           /* nothing to do; return the original string */
           return return_self(self);
      }


I'm not sure the current behavior can be considered better than what
David proposes, but I also wonder whether it matters at all.