diff -r 3877bf2e3235 Lib/posixpath.py
--- a/Lib/posixpath.py	Mon Mar 12 09:46:44 2012 -0700
+++ b/Lib/posixpath.py	Mon Mar 12 14:39:41 2012 -0700
@@ -248,7 +248,10 @@
     if i == 1:
         if 'HOME' not in os.environ:
             import pwd
-            userhome = pwd.getpwuid(os.getuid()).pw_dir
+            try:
+                userhome = pwd.getpwuid(os.getuid()).pw_dir
+            except KeyError:
+                userhome = '/'
         else:
             userhome = os.environ['HOME']
     else: