Switch to using six (#1189)

With the Python 2.7 deadline fast approaching, modernize the codebase
making use of the modernize module to switch to using six, as well as
other upcoming features, such as absolute imports . Stop using 2to3
for Travis, yay!

github/Team.py

@@ -41,6 +41,7 @@
 #                                                                              #
 ################################################################################
 
+from __future__ import absolute_import
 import github.GithubObject
 import github.PaginatedList
 
@@ -48,7 +49,8 @@ import github.Repository
 import github.NamedUser
 import github.Organization
 
-import Consts
+from . import Consts
+import six
 
 
 class Team(github.GithubObject.CompletableGithubObject):
@@ -179,7 +181,7 @@ class Team(github.GithubObject.CompletableGithubObject):
         """
         assert isinstance(member, github.NamedUser.NamedUser), member
         assert role is github.GithubObject.NotSet or isinstance(
-            role, (str, unicode)), role
+            role, (str, six.text_type)), role
         if role is not github.GithubObject.NotSet:
             assert role in ['member', 'maintainer']
             put_parameters = {
@@ -243,10 +245,10 @@ class Team(github.GithubObject.CompletableGithubObject):
         :param privacy: string
         :rtype: None
         """
-        assert isinstance(name, (str, unicode)), name
-        assert description is github.GithubObject.NotSet or isinstance(description, (str, unicode)), description
-        assert permission is github.GithubObject.NotSet or isinstance(permission, (str, unicode)), permission
-        assert privacy is github.GithubObject.NotSet or isinstance(privacy, (str, unicode)), privacy
+        assert isinstance(name, (str, six.text_type)), name
+        assert description is github.GithubObject.NotSet or isinstance(description, (str, six.text_type)), description
+        assert permission is github.GithubObject.NotSet or isinstance(permission, (str, six.text_type)), permission
+        assert privacy is github.GithubObject.NotSet or isinstance(privacy, (str, six.text_type)), privacy
         post_parameters = {
             "name": name,
         }
@@ -269,7 +271,7 @@ class Team(github.GithubObject.CompletableGithubObject):
         :param role: string
         :rtype: :class:`github.PaginatedList.PaginatedList` of :class:`github.NamedUser.NamedUser`
         """
-        assert role is github.GithubObject.NotSet or isinstance(role, (str, unicode)), role
+        assert role is github.GithubObject.NotSet or isinstance(role, (str, six.text_type)), role
         url_parameters = dict()
         if role is not github.GithubObject.NotSet:
             assert role in ['member', 'maintainer', 'all']