Address ResourceWarning warnings

Signed-off-by: JoeLametta <JoeLametta@users.noreply.github.com>

whipper/common/cache.py

@@ -98,17 +98,16 @@ class Persister:
         if not os.path.exists(self._path):
             return
 
-        handle = open(self._path, 'rb')
-        import pickle
-
-        try:
-            self.object = pickle.load(handle)
-            logger.debug('loaded persisted object from %r', self._path)
-        # FIXME: catching too general exception (Exception)
-        except Exception as e:
-            # can fail for various reasons; in that case, pretend we didn't
-            # load it
-            logger.debug(e)
+        with open(self._path, 'rb') as handle:
+            import pickle
+            try:
+                self.object = pickle.load(handle)
+                logger.debug('loaded persisted object from %r', self._path)
+            # FIXME: catching too general exception (Exception)
+            except Exception as e:
+                # can fail for various reasons; in that case, pretend we didn't
+                # load it
+                logger.debug(e)
 
     def delete(self):
         self.object = None