From 4e5740615c2d300b57785126ec84030aadb55445 Mon Sep 17 00:00:00 2001
From: Brad Warren <bmw@eff.org>
Date: Thu, 10 Aug 2017 14:25:08 -0700
Subject: [PATCH] Use util.check_output in Postfix installer

---
 certbot-postfix/certbot_postfix/installer.py      | 13 +++++++++----
 certbot-postfix/certbot_postfix/installer_test.py |  9 ++++-----
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/certbot-postfix/certbot_postfix/installer.py b/certbot-postfix/certbot_postfix/installer.py
index 3de96d9a5..44f77227e 100644
--- a/certbot-postfix/certbot_postfix/installer.py
+++ b/certbot-postfix/certbot_postfix/installer.py
@@ -13,6 +13,8 @@ from certbot import util as certbot_util
 from certbot.plugins import common as plugins_common
 from certbot.plugins import util as plugins_util
 
+from certbot_postfix import util
+
 
 logger = logging.getLogger(__name__)
 
@@ -240,10 +242,13 @@ class Installer(plugins_common.Plugin):
 
         """
         # Parse Postfix version number (feature support, syntax changes etc.)
-        cmd = subprocess.Popen([self.conf('config-utility'), '-d', 'mail_version'],
-                                   stdout=subprocess.PIPE)
-        stdout, _ = cmd.communicate()
-        if cmd.returncode != 0:
+        try:
+            stdout = util.check_output(
+                [self.conf('config-utility'), '-d', 'mail_version'])
+        except subprocess.CalledProcessError:
+            logger.debug(
+                'Encountered an error when trying to determine Postfix version.',
+                exc_info=True)
             raise errors.PluginError('Unable to determine Postfix version.')
 
         # grabs version component of string like "mail_version = 2.11.3"
diff --git a/certbot-postfix/certbot_postfix/installer_test.py b/certbot-postfix/certbot_postfix/installer_test.py
index 9c8aa4f77..a0aa060e8 100644
--- a/certbot-postfix/certbot_postfix/installer_test.py
+++ b/certbot-postfix/certbot_postfix/installer_test.py
@@ -84,12 +84,11 @@ class TestPostfixConfigGenerator(unittest.TestCase):
         """
         installer = self._create_installer()
 
+        check_output_path = "certbot_postfix.installer.util.check_output"
         exe_exists_path = "certbot_postfix.installer.certbot_util.exe_exists"
-        popen_path = "certbot_postfix.installer.subprocess.Popen"
-        with mock.patch(exe_exists_path, return_value=True) as mock_exe_exists:
-            with mock.patch(popen_path) as mock_popen:
-                mock_popen().returncode = 0
-                mock_popen().communicate.return_value = ("mail_version = 3.1.4", "")
+        with mock.patch(check_output_path) as mock_check_output:
+            with mock.patch(exe_exists_path, return_value=True):
+                mock_check_output.return_value = "mail_version = 3.1.4"
                 installer.prepare()
 
         return installer