This reverts r63675 based on the discussion in this thread:

 http://mail.python.org/pipermail/python-dev/2008-June/079988.html

Python 2.6 should stick with PyString_* in its codebase.  The PyBytes_* names
in the spirit of 3.0 are available via a #define only.  See the email thread.
diff --git a/Modules/grpmodule.c b/Modules/grpmodule.c
index 74bf0dc..e5b9f47 100644
--- a/Modules/grpmodule.c
+++ b/Modules/grpmodule.c
@@ -47,7 +47,7 @@
         return NULL;
     }
     for (member = p->gr_mem; *member != NULL; member++) {
-        PyObject *x = PyBytes_FromString(*member);
+        PyObject *x = PyString_FromString(*member);
         if (x == NULL || PyList_Append(w, x) != 0) {
             Py_XDECREF(x);
             Py_DECREF(w);
@@ -58,13 +58,13 @@
     }
 
 #define SET(i,val) PyStructSequence_SET_ITEM(v, i, val)
-    SET(setIndex++, PyBytes_FromString(p->gr_name));
+    SET(setIndex++, PyString_FromString(p->gr_name));
 #ifdef __VMS
     SET(setIndex++, Py_None);
     Py_INCREF(Py_None);
 #else
     if (p->gr_passwd)
-	    SET(setIndex++, PyBytes_FromString(p->gr_passwd));
+	    SET(setIndex++, PyString_FromString(p->gr_passwd));
     else {
 	    SET(setIndex++, Py_None);
 	    Py_INCREF(Py_None);
@@ -113,7 +113,7 @@
     py_str_name = PyObject_Str(pyo_name);
     if (!py_str_name)
 	    return NULL;
-    name = PyBytes_AS_STRING(py_str_name);
+    name = PyString_AS_STRING(py_str_name);
     
     if ((p = getgrnam(name)) == NULL) {
 	PyErr_Format(PyExc_KeyError, "getgrnam(): name not found: %s", name);