Compatibility with guzzle 7.

src/Behat/MinkExtension/ServiceContainer/Driver/GoutteFactory.php

@@ -10,6 +10,7 @@
 
 namespace Behat\MinkExtension\ServiceContainer\Driver;
 
+use GuzzleHttp\ClientInterface;
 use Symfony\Component\Config\Definition\Builder\ArrayNodeDefinition;
 use Symfony\Component\DependencyInjection\Definition;
 
@@ -116,7 +117,8 @@ private function isGoutte1()
     {
         $refl = new \ReflectionParameter(array('Goutte\Client', 'setClient'), 0);
 
-        if ($refl->getClass() && 'Guzzle\Http\ClientInterface' === $refl->getClass()->getName()) {
+        $type = $refl->getType();
+        if ($type instanceof \ReflectionNamedType && 'Guzzle\Http\ClientInterface' === $type->getName()) {
             return true;
         }
 
@@ -125,7 +127,18 @@ private function isGoutte1()
 
     private function isGuzzle6()
     {
-        return interface_exists('GuzzleHttp\ClientInterface') &&
-            version_compare(\GuzzleHttp\ClientInterface::VERSION, '6.0.0', '>=');
+        if (!interface_exists(ClientInterface::class)) {
+            return false;
+        }
+        $rc = new \ReflectionClass(ClientInterface::class);
+        // This constant was removed in Guzzle 7.
+        if ($rc->hasConstant('VERSION')) {
+            return version_compare(ClientInterface::VERSION, '6.0.0', '>=');
+        }
+        // This constant was added in Guzzle 7.
+        if ($rc->hasConstant('MAJOR_VERSION')) {
+            ClientInterface::MAJOR_VERSION >= 6;
+        }
+        return false;
     }
 }