Laravel 5.4 not working on PHP 7.0 due to Doctrine package

I'm trying to deploy a Laravel application on an AWS PHP 7.0 instance (Elastic Beanstalk, but that doesn't really matter).

I get the following error

+ composer.phar install --no-ansi --no-interaction
Do not run Composer as root/super user! See http://ift.tt/1UioBPp for details
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for doctrine/instantiator 1.1.0 -> satisfiable by doctrine/instantiator[1.1.0].
    - doctrine/instantiator 1.1.0 requires php ^7.1 -> your PHP version (7.0.16) does not satisfy that requirement.
  Problem 2
    - doctrine/instantiator 1.1.0 requires php ^7.1 -> your PHP version (7.0.16) does not satisfy that requirement.
    - phpunit/phpunit-mock-objects 3.4.4 requires doctrine/instantiator ^1.0.2 -> satisfiable by doctrine/instantiator[1.1.0].
    - Installation request for phpunit/phpunit-mock-objects 3.4.4 -> satisfiable by phpunit/phpunit-mock-objects[3.4.4].
 (Executor::NonZeroExitStatus)

Any ideas how can I suppress this or get around it on PHP 7.0?

My composer.json

{
    "name": "myapp",
    "description": "My App.",
    "keywords": ["framework", "laravel", "lumen"],
    "license": "MIT",
    "type": "project",
    "require": {
        "php": ">=5.6.4",
        "laravel/lumen-framework": "5.4.*",
        "vlucas/phpdotenv": "~2.2",
        "romanpitak/nginx-config-processor": "^0.2.1",
        "symfony/stopwatch": "^3.2",
        "comodojo/zip": "^2.1",
        "riimu/kit-pathjoin": "1.*",
        "aws/aws-sdk-php": "^3.25",
        "spatie/url": "dev-master"
    },
    "require-dev": {
        "fzaninotto/faker": "~1.4",
        "phpunit/phpunit": "~5.0",
        "mockery/mockery": "~0.9"
    },
    "autoload": {
        "psr-4": {
            "App\\": "app/"
        }
    },
    "autoload-dev": {
        "classmap": [
            "tests/",
            "database/"
        ]
    },
    "scripts": {
        "post-root-package-install": [
            "php -r \"copy('.env.example', '.env');\""
        ]
    },
    "minimum-stability": "dev",
    "prefer-stable": true
}

P.s. I am not using any unit testing. I tried to get rid of the "require-dev" packages and still the same error.

via Chebli Mohamed