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"""

lib/pytz/lazy.py

@@ -61,7 +61,7 @@ class LazyDict(DictMixin):
                     self._fill()
             finally:
                 _fill_lock.release()
-        return self.data.keys()
+        return list(self.data.keys())
 
 
 class LazyList(list):

lib/pytz/tzfile.py

@@ -4,7 +4,7 @@ $Id: tzfile.py,v 1.8 2004/06/03 00:15:24 zenzen Exp $
 '''
 
 try:
-    from cStringIO import StringIO
+    from io import StringIO
 except ImportError:
     from io import StringIO
 from datetime import datetime, timedelta

lib/pytz/tzinfo.py

@@ -548,7 +548,7 @@ def unpickler(zone, utcoffset=None, dstoffset=None, tzname=None):
     # See if we can find an entry differing only by tzname. Abbreviations
     # get changed from the initial guess by the database maintainers to
     # match reality when this information is discovered.
-    for localized_tz in tz._tzinfos.values():
+    for localized_tz in list(tz._tzinfos.values()):
         if (localized_tz._utcoffset == utcoffset
                 and localized_tz._dst == dstoffset):
             return localized_tz