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/Commit.py

@@ -32,6 +32,7 @@
 #                                                                              #
 ################################################################################
 
+from __future__ import absolute_import
 import github.GithubObject
 import github.PaginatedList
 
@@ -42,6 +43,7 @@ import github.CommitCombinedStatus
 import github.File
 import github.CommitStats
 import github.CommitComment
+import six
 
 
 class Commit(github.GithubObject.CompletableGithubObject):
@@ -141,10 +143,10 @@ class Commit(github.GithubObject.CompletableGithubObject):
         :param position: integer
         :rtype: :class:`github.CommitComment.CommitComment`
         """
-        assert isinstance(body, (str, unicode)), body
-        assert line is github.GithubObject.NotSet or isinstance(line, (int, long)), line
-        assert path is github.GithubObject.NotSet or isinstance(path, (str, unicode)), path
-        assert position is github.GithubObject.NotSet or isinstance(position, (int, long)), position
+        assert isinstance(body, (str, six.text_type)), body
+        assert line is github.GithubObject.NotSet or isinstance(line, six.integer_types), line
+        assert path is github.GithubObject.NotSet or isinstance(path, (str, six.text_type)), path
+        assert position is github.GithubObject.NotSet or isinstance(position, six.integer_types), position
         post_parameters = {
             "body": body,
         }
@@ -170,10 +172,10 @@ class Commit(github.GithubObject.CompletableGithubObject):
         :param context: string
         :rtype: :class:`github.CommitStatus.CommitStatus`
         """
-        assert isinstance(state, (str, unicode)), state
-        assert target_url is github.GithubObject.NotSet or isinstance(target_url, (str, unicode)), target_url
-        assert description is github.GithubObject.NotSet or isinstance(description, (str, unicode)), description
-        assert context is github.GithubObject.NotSet or isinstance(context, (str, unicode)), context
+        assert isinstance(state, (str, six.text_type)), state
+        assert target_url is github.GithubObject.NotSet or isinstance(target_url, (str, six.text_type)), target_url
+        assert description is github.GithubObject.NotSet or isinstance(description, (str, six.text_type)), description
+        assert context is github.GithubObject.NotSet or isinstance(context, (str, six.text_type)), context
         post_parameters = {
             "state": state,
         }