Extremely basic first crack at implementing djb's redo.

And a test program.

helpers.py

@@ -0,0 +1,22 @@
+import sys, os, errno
+
+
+def log(s):
+    sys.stdout.flush()
+    sys.stderr.write(s)
+    sys.stderr.flush()
+
+
+def unlink(f):
+    """Delete a file at path 'f' if it currently exists.
+
+    Unlike os.unlink(), does not throw an exception if the file didn't already
+    exist.
+    """
+    try:
+        os.unlink(f)
+    except OSError, e:
+        if e.errno == errno.ENOENT:
+            pass  # it doesn't exist, that's what you asked for
+
+