bug #19842 [FrameworkBundle] Check for class existence before is_subclass_of (chalasr)

This PR was merged into the 2.7 branch.

Discussion
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[FrameworkBundle] Check for class existence before is_subclass_of

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Same as #19342

Commits
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8a9e0f5 [FrameworkBundle] Check for class existence before is_subclass_of

Author: nicolas-grekas

DependencyInjection/Compiler/AddConsoleCommandPass.php

@@ -38,6 +38,10 @@ public function process(ContainerBuilder $container)
 
             $class = $container->getParameterBag()->resolveValue($definition->getClass());
             if (!is_subclass_of($class, 'Symfony\\Component\\Console\\Command\\Command')) {
+                if (!class_exists($class, false)) {
+                    throw new \InvalidArgumentException(sprintf('Class "%s" used for service "%s" cannot be found.', $class, $id));
+                }
+
                 throw new \InvalidArgumentException(sprintf('The service "%s" tagged "console.command" must be a subclass of "Symfony\\Component\\Console\\Command\\Command".', $id));
             }
             $container->setAlias('console.command.'.strtolower(str_replace('\\', '_', $class)), $id);