Infra: Advertise and test Python 3 compatibility

- Add 3.3 - 3.6 to tox.ini
- Add .travis.yml for Travis CI
- Add 3.3 - 3.6 to Trove classifiers
- Add Python version checking to setup.py

.travis.yml

@@ -0,0 +1,25 @@
+language: python
+
+python:
+- '2.7'
+- '3.3'
+- '3.4'
+- '3.5'
+- '3.6'
+# Note: when updating Python versions, also change setup.py and tox.ini
+
+sudo: false
+
+cache: pip
+
+addons:
+  apt:
+    packages:
+      - ldap-utils
+      - slapd
+
+install:
+  - pip install "pip>=7.1.0"
+  - pip install tox-travis tox
+
+script: tox

setup.py

@@ -4,15 +4,24 @@
 See https://www.python-ldap.org/ for details.
 """
 
+import sys,os
+
 has_setuptools = False
 try:
   from setuptools import setup, Extension
   has_setuptools = True
 except ImportError:
   from distutils.core import setup, Extension
 
-from ConfigParser import ConfigParser
-import sys,os,time
+if sys.version_info[0] == 2 and sys.version_info[1] < 7:
+    raise RuntimeError('This software requires Python 2.7 or 3.x.')
+if sys.version_info[0] >= 3 and sys.version_info < (3, 3):
+    raise RuntimeError('The C API from Python 3.3+ is required.')
+
+if sys.version_info[0] >= 3:
+    from configparser import ConfigParser
+else:
+    from ConfigParser import ConfigParser
 
 sys.path.insert(0, os.path.join(os.getcwd(), 'Lib/ldap'))
 import pkginfo
@@ -59,7 +68,8 @@ class OpenLDAP2:
   kwargs = dict(
     include_package_data = True,
     install_requires = ['setuptools'],
-    zip_safe = False
+    zip_safe = False,
+    python_requires = '>=2.7,!=3.0.*,!=3.1.*,!=3.2.*',
   )
 
 setup(
@@ -88,8 +98,17 @@ class OpenLDAP2:
     'Operating System :: Microsoft :: Windows',
     'Operating System :: POSIX',
     'Programming Language :: C',
+
     'Programming Language :: Python',
     'Programming Language :: Python :: 2',
+    'Programming Language :: Python :: 2.7',
+    'Programming Language :: Python :: 3',
+    'Programming Language :: Python :: 3.3',
+    'Programming Language :: Python :: 3.4',
+    'Programming Language :: Python :: 3.5',
+    'Programming Language :: Python :: 3.6',
+    # Note: when updating Python versions, also change .travis.yml and tox.ini
+
     'Topic :: Database',
     'Topic :: Internet',
     'Topic :: Software Development :: Libraries :: Python Modules',

tox.ini

@@ -4,7 +4,8 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py27
+# Note: when updating Python versions, also change setup.py and .travis.yml
+envlist = py27,py33,py34,py35,py36
 
 [testenv]
 commands = {envpython} setup.py test