Motivation
RFC 1945 (see section 3.1) says that request lines may not have a version in which case the request is assumed to be HTTP/0.9. We don't necessarily want to support that but the existing Exception should indicate the possibility of the request being HTTP/0.9 and give the user a chance to track it down.
Modifications
Indicate in the Exception's message that the request is possibly HTTP/0.9.
Result
Fixes#6739
b419bd152a