Merge branch '5.3' into 5.4

* 5.3:
  [Ldap] Fix test
  Remove flex from appveyor

Author: nicolas-grekas

Tests/Security/CheckLdapCredentialsListenerTest.php

@@ -222,26 +222,28 @@ private function createListener()
     }
 }
 
-class TestAuthenticator implements AuthenticatorInterface
-{
-    public function supports(Request $request): ?bool
+if (interface_exists(AuthenticatorInterface::class)) {
+    class TestAuthenticator implements AuthenticatorInterface
     {
-    }
+        public function supports(Request $request): ?bool
+        {
+        }
 
-    public function authenticate(Request $request): Passport
-    {
-    }
+        public function authenticate(Request $request): Passport
+        {
+        }
 
-    public function createAuthenticatedToken(PassportInterface $passport, string $firewallName): TokenInterface
-    {
-    }
+        public function createAuthenticatedToken(PassportInterface $passport, string $firewallName): TokenInterface
+        {
+        }
 
-    public function onAuthenticationSuccess(Request $request, TokenInterface $token, string $firewallName): ?Response
-    {
-    }
+        public function onAuthenticationSuccess(Request $request, TokenInterface $token, string $firewallName): ?Response
+        {
+        }
 
-    public function onAuthenticationFailure(Request $request, AuthenticationException $exception): ?Response
-    {
+        public function onAuthenticationFailure(Request $request, AuthenticationException $exception): ?Response
+        {
+        }
     }
 
     public function createToken(Passport $passport, string $firewallName): TokenInterface