setup.py: Add 'python_requires' in config.

1 files changed, 1 insertions, 0 deletions

diff --git a/setup.py b/setup.py
index 7c102e4..f9ed5ff 100644
--- a/setup.py
+++ b/setup.py
@@ -41,6 +41,7 @@ config = {
     ],
     'keywords': 'acme letsencrypt acmens',
     'py_modules': ['acmens'],
+    'python_requires': '>=3',
     'entry_points': {
         'console_scripts': ['acmens = acmens:main']
     }