Drop 2to3 build step; make all code compatible with all Pythons

Make all library code compatible with both Python 2 and Python 3. Helps
move to modern Python idioms. Can now write for Python 3 (with
workarounds for Python 2) instead of the other way around.

In the future, when it is eventually time to drop Python 2, the library
will be in a better position to remove workarounds

Added a very small comparability module compat.py where required. It
includes definitions for:

- text_type -- A type. str on Python 3. unicode on Python 2.
- string_types -- A tuple. Contains only str on Python 3. Contains str &
                  unicode on Python 2.

1 files changed, 1 insertions, 1 deletions

diff --git a/scripts/make_errorcodes.py b/scripts/make_errorcodes.py
index adc6ee8..aa5e4cd 100755
--- a/scripts/make_errorcodes.py
+++ b/scripts/make_errorcodes.py
@@ -159,7 +159,7 @@ def fetch_errors(versions):
         # https://github.com/postgres/postgres/commit/28e0727076
         errors['55']['55P04'] = 'UNSAFE_NEW_ENUM_VALUE_USAGE'
 
-        for c, cerrs in e1.iteritems():
+        for c, cerrs in e1.items():
             errors[c].update(cerrs)
 
     return classes, errors