Make kolla_set_configs open files in binary mode

This fixes comparisons when files are not Unicode-encoded.

A relevant unit test is included.
It can be used as a base for other _cmp_file method unit tests
if the need arises.

Change-Id: Ic638516eb92d24ad247a7866fd1b5e2ac0400388
Closes-Bug: #1913952

docker/base/set_configs.py

@@ -164,7 +164,7 @@ class ConfigFile(object):
                 not os.path.exists(dest)):
             return False
         # check content
-        with open(source) as f1, open(dest) as f2:
+        with open(source, 'rb') as f1, open(dest, 'rb') as f2:
             if f1.read() != f2.read():
                 LOG.error('The content of source file(%s) and'
                           ' dest file(%s) are not equal.', source, dest)

releasenotes/notes/bug-1913952-a23431cef137f9c7.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes an issue with the ``kolla_set_configs --check`` command when
+    the compared files are non-Unicode.
+    `LP#1913952 <https://launchpad.net/bugs/1913952>`__

tests/test_set_config.py

@@ -339,3 +339,26 @@ class ConfigFileTest(base.BaseTestCase):
         mock_cmp_dir.assert_called_once_with(
             '/var/lib/kolla/config_files/bar', '/foo')
         mock_cmp_file.assert_not_called()
+
+    @mock.patch('grp.getgrgid', autospec=True)
+    @mock.patch('pwd.getpwuid', autospec=True)
+    @mock.patch('os.stat', autospec=True)
+    @mock.patch('builtins.open', new_callable=mock.mock_open)
+    @mock.patch('os.path.exists', autospec=True)
+    def test_cmp_file_opens_both_files_rb(self, mock_os_exists, mock_open,
+                                          mock_os_stat, mock_pwd_getpwuid,
+                                          mock_grp_getgrgid):
+        config_file = set_configs.ConfigFile(
+            '/var/lib/kolla/config_files/bar', '/foo', 'user1', '0644')
+
+        mock_os_exists.return_value = True
+        mock_os_stat.return_value.st_mode = int('0o100644', 8)
+        mock_pwd_getpwuid.return_value.pw_name = 'user1'
+        mock_grp_getgrgid.return_value.gr_name = 'user1'
+
+        self.assertIs(True,
+                      config_file._cmp_file('/fake/file1', '/fake/file2'))
+
+        self.assertEqual([mock.call('/fake/file1', 'rb'),
+                          mock.call('/fake/file2', 'rb')],
+                         mock_open.call_args_list)