[PR #9579/0de39a6f backport][stable-10] use open() as context manager (#9596)

use open() as context manager (#9579)

* use open() as context manager

* add changelog frag

(cherry picked from commit 0de39a6f47)

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

plugins/module_utils/known_hosts.py

@@ -103,13 +103,11 @@ def not_in_host_file(self, host):
             continue
 
         try:
-            host_fh = open(hf)
+            with open(hf) as host_fh:
+                data = host_fh.read()
         except IOError:
             hfiles_not_found += 1
             continue
-        else:
-            data = host_fh.read()
-            host_fh.close()
 
         for line in data.split("\n"):
             if line is None or " " not in line: