Error: no header found

When pasting in a message to the DECRYPT window in keybase.io, I sometimes get

Error: No Header Found

What I found is that if I miss one of the dashes in the paste, that causes problem. And rightly so!

Not sure if it makes sense to report back to the user that the header is ALMOST there, but the missed-dash-in-past-of-header bit me a few times.

4 dashes and 5 dashes looks almost the same to a human. "No header found! I'm looking right at it!"

UI experts can debate whether a loose match of the PGP header is a blatant violation of the spec of a helpful assist to a careless human.

Start by reproducing the missing-dash case in the DECRYPT window and reading the client code that produces “No Header Found.” The issue names no files or tests, so first identify the relevant error-handling entry point. Done would require an agreed user-facing response for nearly valid PGP headers and coverage for the malformed-header case.

Written by the indexing model from the issue text.