Merge branch '2.7' into 2.8

* 2.7:
  [HttpFoundation] Use the correct syntax for session gc based on Pdo driver
  Revert "bug #24987 [Console] Fix global console flag when used in chain (Simperfit)"
  Revert "bug #25487 [Console] Fix a bug when passing a letter that could be an alias (Simperfit)"
  Disable CSP header on exception pages only in debug
  Fixed submitting disabled buttons
  Fixed Button::setParent() when already submitted
  Improve assertions
  SCA: get rid of repetitive calls
  allow null values for root nodes in YAML configs
  [VarDumper] Fix docblock
  Improve phpdoc to make it more explicit

Author: fabpot

Tests/FinderTest.php

@@ -12,7 +12,6 @@
 namespace Symfony\Component\Finder\Tests;
 
 use Symfony\Component\Finder\Adapter\AdapterInterface;
-use Symfony\Component\Finder\Adapter\GnuFindAdapter;
 use Symfony\Component\Finder\Adapter\PhpAdapter;
 use Symfony\Component\Finder\Finder;
 
@@ -620,15 +619,15 @@ public function testAdapterSelection()
     {
         // test that by default, PhpAdapter is selected
         $adapters = Finder::create()->getAdapters();
-        $this->assertTrue($adapters[0] instanceof PhpAdapter);
+        $this->assertInstanceOf('Symfony\Component\Finder\Adapter\PhpAdapter', $adapters[0]);
 
         // test another adapter selection
         $adapters = Finder::create()->setAdapter('gnu_find')->getAdapters();
-        $this->assertTrue($adapters[0] instanceof GnuFindAdapter);
+        $this->assertInstanceOf('Symfony\Component\Finder\Adapter\GnuFindAdapter', $adapters[0]);
 
         // test that useBestAdapter method removes selection
         $adapters = Finder::create()->useBestAdapter()->getAdapters();
-        $this->assertFalse($adapters[0] instanceof PhpAdapter);
+        $this->assertNotInstanceOf('Symfony\Component\Finder\Adapter\PhpAdapter', $adapters[0]);
     }
 
     public function getTestPathData()