Merge branch '6.4' into 7.0

* 6.4:
  [Scheduler] Throw an exception when no dispatcher has been passed to a Schedule
  [Mime] Fix TextPart using an unknown File
  Fix autoload configs to avoid warnings when building optimized autoloaders

Author: fabpot

Diff for: composer.json

@@ -32,7 +32,8 @@
         "files": [ "bootstrap.php" ],
         "psr-4": { "Symfony\\Bridge\\PhpUnit\\": "" },
         "exclude-from-classmap": [
-            "/Tests/"
+            "/Tests/",
+            "/bin/"
         ]
     },
     "bin": [