bug #2263 Allow to specify Throwable as exception class (a-menshchikov)

This PR was merged into the 2.x branch.

Discussion
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Allow to specify Throwable as exception class

Currently we can't use Throwable in exception.codes because check method uses `is_subclass_of`.
This PR fixes this issue.

Commits
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a1c9138 Allow to specify Throwable as exception class

Author: xabbuh

DependencyInjection/Configuration.php

@@ -561,7 +561,7 @@ private function addExceptionSection(ArrayNodeDefinition $rootNode)
 
     private function testExceptionExists(string $throwable)
     {
-        if (!is_subclass_of($throwable, \Throwable::class)) {
+        if (!is_a($throwable, \Throwable::class, true)) {
             throw new InvalidConfigurationException(sprintf('FOSRestBundle exception mapper: Could not load class "%s" or the class does not extend from "%s". Most probably this is a configuration problem.', $throwable, \Throwable::class));
         }
     }

Tests/DependencyInjection/ConfigurationTest.php

@@ -48,6 +48,7 @@ public function testExceptionCodesAcceptsIntegers()
         $expectedConfig = [
             \RuntimeException::class => 500,
             \TypeError::class => 500,
+            \Throwable::class => 500,
         ];
 
         $config = $this->processor->processConfiguration(