Use the system zoneinfo from sys-libs/timezone-data.

--- pytz/__init__.py
+++ pytz/__init__.py
@@ -54,8 +54,7 @@
     for part in name_parts:
         if part == os.path.pardir or os.path.sep in part:
             raise ValueError('Bad path segment: %r' % part)
-    filename = os.path.join(os.path.dirname(__file__),
-                            'zoneinfo', *name_parts)
+    filename = os.path.join('/usr/share/zoneinfo', *name_parts)
     if not os.path.exists(filename) and resource_stream is not None:
         # http://bugs.launchpad.net/bugs/383171 - we avoid using this
         # unless absolutely necessary to help when a broken version of