Patch from M.-A. Lemburg:
Python on UNIX now trusts PYTHONHOME unconditionally

Modules/getpath.c:

Landmark changed to os.py.

Setting PYTHONHOME now unconditionally sets sys.prefix
(and sys.exec_prefix). No further checks are done whether the
standard lib can be found in that location or not. This is in
sync with the PC subdir getpath implementations.

PC/getpathp.c:

Landmark changed to os.py.

PC/os2vacpp/getpathp.c:

Landmark changed to os.py.

Note: BAW's checkin on exceptions.c eliminates earlier concerns about
a bogus PYTHONHOME value leading to a core dump.  Instead it causes a
useless sys.path and prevents imports.
diff --git a/PC/os2vacpp/getpathp.c b/PC/os2vacpp/getpathp.c
index b7056ab..a4a4d0e 100644
--- a/PC/os2vacpp/getpathp.c
+++ b/PC/os2vacpp/getpathp.c
@@ -68,14 +68,14 @@
  *
  * Otherwise, if there is a PYTHONPATH environment variable, we return that.
  *
- * Otherwise we try to find $progpath/lib/string.py, and if found, then
+ * Otherwise we try to find $progpath/lib/os.py, and if found, then
  * root is $progpath/lib, and we return Python path as compiled PYTHONPATH
  * with all "./lib" replaced by $root (as above).
  *
  */
 
 #ifndef LANDMARK
-#define LANDMARK "lib\\string.py"
+#define LANDMARK "lib\\os.py"
 #endif
 
 static char prefix[MAXPATHLEN+1];