don't log Mastodon 502 errors.

Building in CSRF prevention

active_bots/mastodonbot.py

@@ -2,7 +2,7 @@
 
 from bot import Bot
 import logging
-from mastodon import Mastodon
+from mastodon import Mastodon, MastodonAPIError
 import re
 from report import Report
 
@@ -25,7 +25,13 @@ class MastodonBot(Bot):
             return mentions
         try:
             notifications = m.notifications()
-        except Exception:
+        except MastodonAPIError:
+            # Not tested yet, as we don't have a dysfunctional Mastodon instance.
+            for arg in MastodonAPIError.args:
+                if arg == 502:
+                    # Don't log 502 errors
+                    return mentions
+
             logger.error("Unknown Mastodon API Error.", exc_info=True)
             return mentions
         for status in notifications: