title: Upgrading Symfony project from 3.2 to 3.4
body: <p>I am trying to upgrade Symfony on Windows 10 machine. Current version is 3.2. I've updated the <code>composer.json</code> package to <code>"symfony/symfony": "3.4.*"</code>. Then I ran <code>composer update symfony/symfony</code> and got the following error message:</p>
  
  <pre><code>The requested package symfony/symfony 3.4.* exists as symfony/symfony[v3.2.2] but these are rejected by your constraint.
  </code></pre>
  
  <p>Any ideas what can be the problem? Thanks!</p>
  
  <p>Here is the <code>composer.json</code> file:</p>
  
  <pre><code>{
      "name": "martin/editor",
      "license": "proprietary",
      "type": "project",
      "autoload": {
          "psr-4": {
              "": "src/"
          },
          "classmap": [
              "app/AppKernel.php",
              "app/AppCache.php"
          ]
      },
      "autoload-dev": {
          "psr-4": {
              "Tests\\": "tests/"
          }
      },
      "require": {
          "php": "&gt;=5.5.9",
          "symfony/symfony": "3.4.*",
          "doctrine/orm": "^2.5",
          "doctrine/doctrine-bundle": "^1.6",
          "doctrine/doctrine-cache-bundle": "^1.2",
          "symfony/swiftmailer-bundle": "^2.3.10",
          "symfony/monolog-bundle": "^3.0.2",
          "symfony/polyfill-apcu": "^1.0",
          "sensio/distribution-bundle": "^5.0",
          "sensio/framework-extra-bundle": "^3.0.2",
          "incenteev/composer-parameter-handler": "^2.0",
          "mikehaertl/php-shellcommand": "&gt;=1.2.4",
          "phpoffice/phpspreadsheet": "*"
      },
      "require-dev": {
          "sensio/generator-bundle": "^3.0",
          "symfony/phpunit-bridge": "^3.0"
      },
      "scripts": {
          "symfony-scripts": [
              "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
              "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
              "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
              "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
              "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile",
              "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"
          ],
          "post-install-cmd": [
              "@symfony-scripts"
          ],
          "post-update-cmd": [
              "@symfony-scripts"
          ]
      },
      "extra": {
          "symfony-app-dir": "app",
          "symfony-bin-dir": "bin",
          "symfony-var-dir": "var",
          "symfony-web-dir": "web",
          "symfony-tests-dir": "tests",
          "symfony-assets-install": "relative",
          "incenteev-parameters": {
              "file": "app/config/parameters.yml"
          },
          "branch-alias": null
      },
      "repositories": [{
          "type": "composer",
          "url": "https:\/\/www.phpclasses.org\/"
      }, {
          "packagist": false
      }, {
          "type": "vcs",
          "url": "https://github.com/mikehaertl/php-shellcommand"
      }, {
          "type": "vcs",
          "url": "https://github.com/PHPOffice/PhpSpreadsheet"
      }, {
          "type": "vcs",
          "url": "https://github.com/php-fig/simple-cache"
      }
      ]
  }
  </code></pre>