Verification: stop kicking members on suspicious 403

A Discord error code 50_0007 signifies that the DM dispatch failed
because the target user does not accept DMs from the bot.
Such errors are ignored as before.

Any other 403s will however cause the bot to stop making requests.
This is in case the bot gets caught by an anti-spam filter and
should immediately stop.

1 files changed, 16 insertions, 1 deletions

diff --git a/bot/cogs/verification.py b/bot/cogs/verification.py
index d5216c7c0..196808b0d 100644
--- a/bot/cogs/verification.py
+++ b/bot/cogs/verification.py
@@ -87,6 +87,14 @@ MENTION_UNVERIFIED = discord.AllowedMentions(roles=[discord.Object(constants.Rol
 Request = t.Callable[[discord.Member], t.Awaitable]
 
 
+class StopExecution(Exception):
+    """Signals that a task should halt immediately & alert admins."""
+
+    def __init__(self, reason: discord.HTTPException) -> None:
+        super().__init__()
+        self.reason = reason
+
+
 class Limit(t.NamedTuple):
     """Composition over config for throttling requests."""
 
@@ -277,6 +285,9 @@ class Verification(Cog):
                 continue
             try:
                 await request(member)
+            except StopExecution as stop_execution:
+                await self._alert_admins(stop_execution.reason)
+                break
             except discord.HTTPException as http_exc:
                 bad_statuses.add(http_exc.status)
             else:
@@ -304,8 +315,12 @@ class Verification(Cog):
 
         async def kick_request(member: discord.Member) -> None:
             """Send `KICKED_MESSAGE` to `member` and kick them from the guild."""
-            with suppress(discord.Forbidden):
+            try:
                 await member.send(KICKED_MESSAGE)
+            except discord.Forbidden as exc_403:
+                log.trace(f"DM dispatch failed on 403 error with code: {exc_403.code}")
+                if exc_403.code != 50_007:  # 403 raised for any other reason than disabled DMs
+                    raise StopExecution(reason=exc_403)
             await member.kick(reason=f"User has not verified in {KICKED_AFTER} days")
 
         n_kicked = await self._send_requests(members, kick_request, Limit(batch_size=2, sleep_secs=1))