Merge branch '4.1' into 4.2

* 4.1:
  bump required Twig version
  fix compatibility with Twig >= 2.6.1
  [Form] SA fix
  fix compatibility with PHPUnit 4.8
  remove return type hint for PHP 5 compatibility
  SCA: minor code tweaks
  Component CssSelector tests
  [DebugClassLoader] Readd findFile() method
  [Console] Fix composer.json suggest/provide
  Revert "bug #29597 [DI] fix reporting bindings on overriden services as unused (nicolas-grekas)"
  Fixed exception wording
  Fix SwiftMailerHandler to support Monolog's latest reset functionality

Author: fabpot

composer.json

@@ -28,11 +28,14 @@
         "symfony/process": "~3.4|~4.0",
         "psr/log": "~1.0"
     },
+    "provide": {
+        "psr/log-implementation": "1.0"
+    },
     "suggest": {
         "symfony/event-dispatcher": "",
         "symfony/lock": "",
         "symfony/process": "",
-        "psr/log-implementation": "For using the console logger"
+        "psr/log": "For using the console logger"
     },
     "conflict": {
         "symfony/dependency-injection": "<3.4",