Add missing dependency from previous author's repo:

http://stromberg.dnsalias.org/~strombrg/backshift/documentation/html/module-tree.html

python2x3.py

@@ -0,0 +1,66 @@
+# coding=utf-8
+#!/usr/bin/env python
+
+# pylint: disable=invalid-name
+# invalid-name: We define a few global-scope constants in lower case.  Deal with it.
+
+'''Provides code and data to facilitate writing python code that runs on 2.x and 3.x, including pypy'''
+
+# I'm afraid pylint won't like this one...
+
+import sys
+
+
+def python_major():
+    '''Return an integer corresponding to the major version # of the python interpreter we're running on'''
+    # This originally used the platform module, but platform fails on IronPython; sys.version seems to work
+    # on everything I've tried
+    result = sys.version_info[0]
+    return result
+
+if python_major() == 2:
+    empty_bytes = ''
+    null_byte = '\0'
+    bytes_type = str
+
+    def intlist_to_binary(intlist):
+        '''Convert a list of integers to a binary string type'''
+        return ''.join(chr(byte) for byte in intlist)
+
+    def string_to_binary(string):
+        '''Convert a text string to a binary string type'''
+        return string
+
+    def binary_to_intlist(binary):
+        '''Convert a binary string to a list of integers'''
+        return [ord(character) for character in binary]
+
+    def binary_to_string(binary):
+        '''Convert a binary string to a text string'''
+        return binary
+elif python_major() == 3:
+    empty_bytes = ''.encode('utf-8')
+    null_byte = bytes([0])
+    bytes_type = bytes
+
+    def intlist_to_binary(intlist):
+        '''Convert a list of integers to a binary string type'''
+        return bytes(intlist)
+
+    def string_to_binary(string):
+        '''Convert a text string (or binary string type) to a binary string type'''
+        if isinstance(string, str):
+            return string.encode('latin-1')
+        else:
+            return string
+
+    def binary_to_intlist(binary):
+        '''Convert a binary string to a list of integers'''
+        return binary
+
+    def binary_to_string(binary):
+        '''Convert a binary string to a text string'''
+        return binary.decode('latin-1')
+else:
+    sys.stderr.write('%s: Python < 2 or > 3 not (yet) supported\n' % sys.argv[0])
+    sys.exit(1)