bots: Fix RSS bot for Python 3.x support.

- Call `super()` in the init method.
- Change return hashlib.md5 syntax to encode properly for Python 3

Signed-off-by: Manu LN <manu+github@lacavernedemanu.fr>

zulip/integrations/rss/rss-bot

@@ -111,6 +111,7 @@ def log_error_and_exit(error: str) -> None:
 
 class MLStripper(HTMLParser):
     def __init__(self) -> None:
+        super().__init__()
         self.reset()
         self.fed = []  # type: List[str]
 
@@ -128,7 +129,7 @@ def strip_tags(html: str) -> str:
 def compute_entry_hash(entry: Dict[str, Any]) -> str:
     entry_time = entry.get("published", entry.get("updated"))
     entry_id = entry.get("id", entry.get("link"))
-    return hashlib.md5(entry_id + str(entry_time)).hexdigest()
+    return hashlib.md5((entry_id + str(entry_time)).encode()).hexdigest()
 
 def unwrap_text(body: str) -> str:
     # Replace \n by space if it is preceded and followed by a non-\n.