Feature: Improve error reporting for failed connection attempts and improve cancellation forwarding during DNS lookup, TCP/IP connection or TLS handshake. (#168, #169, #170, #171, #176 and #177 by @clue)

All error messages now always contain a reference to the remote URI to give more details which connection actually failed and the reason for this error. Accordingly, failures during DNS lookup will now mention both the remote URI as well as the DNS error reason. TCP/IP connection issues and errors during a secure TLS handshake will both mention the remote URI as well as the underlying socket error. Similarly, lost/dropped connections during a TLS handshake will now report a lost connection instead of an empty error reason.

For most common use cases this means that simply reporting the Exception message should give the most relevant details for any connection issues:

$promise = $connector->connect('tls://example.com:443');
$promise->then(function (ConnectionInterface $conn) use ($loop) {
    // …
}, function (Exception $e) {
    echo $e->getMessage();
});