Errors
type t =
| NoError
| ProtocolError
| InternalError
| FlowControlError
| SettingsTimeout
| StreamClosed
| FrameSizeError
| RefusedStream
| Cancel
| CompressionError
| ConnectError
| EnhanceYourCalm
| InadequateSecurity
| HTTP_1_1_Required
| UnknownError_code of int32
val to_string : t -> string