nice visual error messages for invalid header values #1897

Job	Run time
compile_and_lint	2m 9s
windows_test	4m 1s
test (postgres, postgres, postgres://root:[email protected]/sqlpage)	1m 53s
test (mysql, mysql, mysql://root:[email protected]/sqlpage)	1m 36s
test (mssql, mssql, mssql://root:[email protected]/sqlpage)	1m 51s
test (odbc, postgres, Driver=PostgreSQL Unicode;Server=127.0.0.1;Port=5432;Database=sqlpage;UID=r...	2m 35s
docker_build (linux/arm/v7)	4m 53s
docker_build (linux/arm64)	5m 22s
docker_build (linux/amd64)	4m 52s
docker_push	18s
	29m 30s

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