您需要将任何以@开头的字符串放在引号中

You need to put any strings starting with @ in quotes:

arguments:
    ["@security.context", "@fos_user.user_manager"]

保留的字符(如@)应加引号. Symfony 2.8中不推荐使用未引用@的. Symfony 3.0将禁止您使用此类定义，并会引发异常.

Reserved characters, like @, should be quoted. Unquoted @s were deprecated in Symfony 2.8. Symfony 3.0 will forbid you to use such definitions and will throw an exception.

如果您无法控制注册有问题的配置的捆绑软件，请向供应商发送包含修复程序的请求请求.作为快速修复，您可以降级Symfony. 2.7和2.8都可以使用(后者只会发出弃用通知).

If you don't have control over the bundle that registered the problematic configuration, send a pull request with a fix to the vendor. As a quick fix you can downgrade Symfony. 2.7 will work, as well as 2.8 (the later will only emit a deprecation notice).