Don't check as often whether the .redo directory exists.

Just check it once after running a subprocess: that's the only way it ought
to be able to disappear (ie. in a 'make clean' setup).

helpers.py

@@ -15,24 +15,6 @@ def unlink(f):
             pass  # it doesn't exist, that's what you asked for
 
 
-def mkdirp(d, mode=None):
-    """Recursively create directories on path 'd'.
-
-    Unlike os.makedirs(), it doesn't raise an exception if the last element of
-    the path already exists.
-    """
-    try:
-        if mode:
-            os.makedirs(d, mode)
-        else:
-            os.makedirs(d)
-    except OSError, e:
-        if e.errno == errno.EEXIST:
-            pass
-        else:
-            raise
-
-
 def log_(s):
     sys.stdout.flush()
     if vars.DEBUG_PIDS: