Add deprecation warning for Python 2.6 (#5391)

* Add deprecation warning for Python 2.6

* Allow disabling Python 2.6 warning

acme/acme/__init__.py

@@ -13,9 +13,10 @@ supported version: `draft-ietf-acme-01`_.
 import sys
 import warnings
 
-if sys.version_info[:2] == (3, 3):
-    warnings.warn(
-            "Python 3.3 support will be dropped in the next release of "
-            "acme. Please upgrade your Python version.",
-            PendingDeprecationWarning,
-    ) #pragma: no cover
+for (major, minor) in [(2, 6), (3, 3)]:
+    if sys.version_info[:2] == (major, minor):
+        warnings.warn(
+                "Python {0}.{1} support will be dropped in the next release of "
+                "acme. Please upgrade your Python version.".format(major, minor),
+                DeprecationWarning,
+        ) #pragma: no cover

certbot/main.py

@@ -4,6 +4,7 @@ import functools
 import logging.handlers
 import os
 import sys
+import warnings
 
 import configobj
 import josepy as jose
@@ -1217,9 +1218,17 @@ def main(cli_args=sys.argv[1:]):
         # Let plugins_cmd be run as un-privileged user.
         if config.func != plugins_cmd:
             raise
-    if sys.version_info[:2] == (3, 3):
-        logger.warning("Python 3.3 support will be dropped in the next release "
-                    "of Certbot - please upgrade your Python version.")
+    deprecation_fmt = (
+        "Python %s.%s support will be dropped in the next "
+        "release of Certbot - please upgrade your Python version.")
+    # We use the warnings system for Python 2.6 and logging for Python 3
+    # because DeprecationWarnings are only reported by default in Python <= 2.6
+    # and warnings can be disabled by the user.
+    if sys.version_info[:2] == (2, 6):
+        warning = deprecation_fmt % sys.version_info[:2]
+        warnings.warn(warning, DeprecationWarning)
+    elif sys.version_info[:2] == (3, 3):
+        logger.warning(deprecation_fmt, *sys.version_info[:2])
 
     set_displayer(config)