Started to work on Python 3 support.

--HG--
branch : trunk
diff --git a/jinja2/bccache.py b/jinja2/bccache.py
index 2786082..6415158 100644
--- a/jinja2/bccache.py
+++ b/jinja2/bccache.py
@@ -28,7 +28,7 @@
 
 
 bc_version = 1
-bc_magic = 'j2' + pickle.dumps(bc_version, 2)
+bc_magic = 'j2'.encode('ascii') + pickle.dumps(bc_version, 2)
 
 
 class Bucket(object):