"Aha, so an overzealous IT network decided to block the request before it even reached my server."
What classifies this as an "overzealous" act of network configuration? There may be a subjectively legitimate reason the user's network was configured this way.
"I had no idea I was ever going to get anything different."
There's an entire list of HTTP status codes. That was your clue that you would get something different. You made a decision to not have handling for them all. Not implementing handling for 418 is understandable, but forbidden and service unavailable responses are common enough.
What classifies this as an "overzealous" act of network configuration? There may be a subjectively legitimate reason the user's network was configured this way.
"I had no idea I was ever going to get anything different."
There's an entire list of HTTP status codes. That was your clue that you would get something different. You made a decision to not have handling for them all. Not implementing handling for 418 is understandable, but forbidden and service unavailable responses are common enough.