The test for partition was too strict, and the SSL3 generator
is quite likely to generate more data whereas the TLS generator
generate the correct amount every time.
now bigger bytestring than necessary are now valid as well.
compared to the normal fromJust, it take an extra string to report
what kind of fromJust we were doing. it's quite valuable when
shuffling code and assertion break.
at some point, it need to be removed completely in favor of better types
that better reflect the actual state on the connection.
