We should gradually phase out our use of unwrap() for graceful error handling or expect(). expect() should only be used for cases where an internal invariant has been violated. All values that go through or come from external crates should never have unwrap() or expect() called on them.

Reasoning: A web engine is an incredibly complicated piece of software that deals with unreliable, and often malicious, input. As much as possible, all operations should be considered fallible and failures handled as best as possible.