some better error handling

replacer.py

@@ -40,7 +40,20 @@ dprint = ContextVar('dprint')
 http = ContextVar('http')
 
 async def handler(request):
+	try:
+		await _handler(request)
+	except aiohttp.ClientConnectorError:
+		raise web.HTTPServiceUnavailable(
+			text=f'{request.host} is temporarily unavailable. Try again later.',
+		)
+
+async def _handler(request):
+	try:
 		hconfig = config['hosts'][request.host]
+	except KeyError:
+		# this should only happen if our reverse proxy is set to proxy everything to us
+		raise web.HTTPNotFound()
+
 	dprint.set(dprint_factory())
 	async with http().request(
 		request.method,