A realtime logging and aggregation server.
Sentry is a modern error logging and aggregation platform.
Sentry is a Server
The Sentry package fundamentally is just a simple server and web UI. It will handle authenticating clients (such as Raven) and all of the logic behind storage and aggregation.
That said, Sentry is not limited to Python. The primary implementation is in Python, but it contains a full API for sending events from any language, in any application.
These screenshots may be slightly outdated, but should give you a feel for what Sentry presents.