Closes:#752602.
* Check hashes of files ourselves rather than running dget to
re-retreive the .dsc.
+ * Check SHA-256 of .dsc against hash from archive_query (ie projectb)
+ rather than letting dpkg-source do a signature verification.
+ Closes:#737619.
+ * Treat .dsc as bytes, just like everything else, rather than letting
+ HTTP::Message convert it to a Perl unicode string which the rest of
+ the program mishandles. Closes:#738536.
Minor improvements:
* Include canonicalised suite name in signed tag message.