Port Python 2 API to Python 3

Copy livestatus Python API from `api/python` to `api/python3` and make
necessary changes to run under Python 3 (somewhat tested on 3.6).

The original GPL'ed sources are from commit
e06cefe.

Signed-off-by: Aksel Sjögren <asjogren@itrsgroup.com>

api/python/example.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2
 # -*- encoding: utf-8; py-indent-offset: 4 -*-
 # +------------------------------------------------------------------+
 # |             ____ _               _        __  __ _  __           |

api/python/example_multisite.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2
 # -*- encoding: utf-8; py-indent-offset: 4 -*-
 # +------------------------------------------------------------------+
 # |             ____ _               _        __  __ _  __           |
@@ -25,6 +25,7 @@
 # Boston, MA 02110-1301 USA.
 
 import os
+import sys
 import livestatus
 
 try:

api/python3/README.md

@@ -0,0 +1,2 @@
+This Python package is a Python 3 port of the Python 2 `livestatus` package.
+See [../python/README](../python/README).

api/python3/__init__.py

@@ -0,0 +1,19 @@
+from .livestatus import (
+    SingleSiteConnection,
+    MultiSiteConnection,
+    MKLivestatusException,
+    MKLivestatusSocketError,
+    MKLivestatusSocketClosed,
+    MKLivestatusQueryError,
+    MKLivestatusNotFoundError,
+)
+
+__all__ = [
+    "SingleSiteConnection",
+    "MultiSiteConnection",
+    "MKLivestatusException",
+    "MKLivestatusSocketError",
+    "MKLivestatusSocketClosed",
+    "MKLivestatusQueryError",
+    "MKLivestatusNotFoundError",
+]