[FIX] runbot_merge: make Sentry middleware delegate to wrapped app

In Odoo 13, the cache middleware was modified to straight hit
`http.root` assuming it's the Odoo root object. When `http.root` is
replaced by a wrapping middleware, the entire thing blows up and shits
the bed.

Patch up by automatically delegating attribute accesses to the wrapped
application (which is probably Root), although why this is not just
folded into Root is getting less and less clear.

runbot_merge/__init__.py

@@ -8,6 +8,9 @@ from sentry_sdk.integrations.wsgi import SentryWsgiMiddleware
 from odoo import http
 from . import models, controllers
 
+def delegate(self, attr):
+    return getattr(self.app, attr)
+SentryWsgiMiddleware.__getattr__ = delegate
 
 def enable_sentry():
     logger = logging.getLogger('runbot_merge')