Frequently people are building worlds and get errors in the build that prevent it from building successfully. That's fine and debuggable, but the SDK will currently still try to launch/upload the world after a failure.
This manifests frequently as questions like:
"Why doesn't X change when I update my world?" or "Why do I get kicked to the default world when I test build or join my uploaded world?"
If it errored out before uploading if the build failed and gave a message to indicate that the user should check the console, that'd probably cut down on a lot of confusion for newer world creators.
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VRC Build: 772 (n/a)
Platform: Windows (Unity)
SDK: VRCSDK-2019.05.16.13.10 (and previous)