Compat for Swiftmailer 6 but preserve compatibility with Swiftmailer 5.

composer.json

@@ -5,7 +5,7 @@
     "license": "MIT",
     "require": {
         "php" : ">=5.3.0",
-        "swiftmailer/swiftmailer": "~5.2"
+        "swiftmailer/swiftmailer": "~5.2|^6.0"
     },
     "require-dev": {
         "psr/log": "*"

lib/mailer/sfMailer.class.php

@@ -239,7 +239,9 @@ public function setDeliveryAddress($address)
    */
   public function compose($from = null, $to = null, $subject = null, $body = null)
   {
-    return Swift_Message::newInstance()
+    $msg = new Swift_Message();
+
+    return $msg
       ->setFrom($from)
       ->setTo($to)
       ->setSubject($subject)
@@ -277,12 +279,12 @@ public function sendNextImmediately()
   /**
    * Sends the given message.
    *
-   * @param Swift_Transport $transport         A transport instance
-   * @param string[]        &$failedRecipients An array of failures by-reference
+   * @param Swift_Mime_Message|Swift_Mime_SimpleMessage $message           The message to send.
+   * @param string[]                                    &$failedRecipients An array of failures by-reference
    *
    * @return int|false The number of sent emails
    */
-  public function send(Swift_Mime_Message $message, &$failedRecipients = null)
+  public function send($message, &$failedRecipients = null)
   {
     if ($this->force)
     {

lib/mailer/sfNoMailer.class.php

@@ -56,7 +56,7 @@ public function sendNextImmediately()
     return null;
   }
 
-  public function send(Swift_Mime_Message $message, &$failedRecipients = null)
+  public function send($message, &$failedRecipients = null)
   {
     return null;
   }