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.

PC/getpathp.c

diff --git a/PC/getpathp.c b/PC/getpathp.c
index 2123b2a..4354853 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -53,7 +53,7 @@
 
    * We attempt to locate the "Python Home" - if the PYTHONHOME env var
      is set, we believe it.  Otherwise, we use the path of our host .EXE's
-     to try and locate our "landmark" (lib\\string.py) and deduce our home.
+     to try and locate our "landmark" (lib\\os.py) and deduce our home.
      - If we DO have a Python Home: The relevant sub-directories (Lib, 
        plat-win, lib-tk, etc) are based on the Python Home
      - If we DO NOT have a Python Home, the core Python Path is
@@ -110,7 +110,7 @@
  */
 
 #ifndef LANDMARK
-#define LANDMARK "lib\\string.py"
+#define LANDMARK "lib\\os.py"
 #endif
 
 static char prefix[MAXPATHLEN+1];