The ".pth" code knew about the layout of Python trees on unix and
windows, but not on the mac. Fixed.
diff --git a/Lib/site.py b/Lib/site.py
index 52ad11d..512f00b 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -122,6 +122,8 @@
                                  "python" + sys.version[:3],
                                  "site-packages"),
                         makepath(prefix, "lib", "site-python")]
+        elif os.sep == ':':
+            sitedirs = [makepath(prefix, "lib", "site-packages")]
         else:
             sitedirs = [prefix]
         for sitedir in sitedirs: