Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/pytz/__init__.py

@@ -40,13 +40,13 @@ from pytz.tzfile import build_tzinfo, _byte_string
 
 
 try:
-    unicode
+    str
 
 except NameError: # Python 3.x
 
     # Python 3.x doesn't have unicode(), making writing code
     # for Python 2.3 and Python 3.x a pain.
-    unicode = str
+    str = str
 
     def ascii(s):
         r"""