Use propper base64 encoding version for py3

Removes py3-only warning (this alias might be removed in future py3 version):

> DeprecationWarning: encodestring() is a deprecated alias, use encodebytes()
>  ('%s:%s' % (username, password)).encode('utf-8')).decode('utf-8').replace('\n', '')

py2-compatible change.

budget/tests.py

@@ -5,7 +5,6 @@ try:
 except ImportError:
     import unittest  # NOQA
 
-import base64
 import os
 import json
 from collections import defaultdict
@@ -17,6 +16,7 @@ from flask import session
 
 import run
 import models
+import utils
 
 
 class TestCase(unittest.TestCase):
@@ -759,7 +759,7 @@ class APITestCase(TestCase):
 
     def get_auth(self, username, password=None):
         password = password or username
-        base64string = base64.encodestring(
+        base64string = utils.base64_encode(
             ('%s:%s' % (username, password)).encode('utf-8')).decode('utf-8').replace('\n', '')
         return {"Authorization": "Basic %s" % base64string}
 

budget/utils.py

@@ -1,3 +1,4 @@
+import base64
 import re
 import inspect
 
@@ -120,3 +121,6 @@ def list_of_dicts2csv(dict_to_convert):
     if six.PY3:
         csv_file = BytesIO(csv_file.getvalue().encode('utf-8'))
     return csv_file
+
+# base64 encoding that works with both py2 and py3 and yield no warning
+base64_encode =  base64.encodestring if six.PY2 else base64.encodebytes