[Flow] Adding an interface leads to "Execution of subprocess failed with exit code 255 and no output"

[Christian Eßl]

Ok. If it makes a difference: 

I installed TYPO3 Flow as described here: 
http://flow.typo3.org/download/release-notes/flow-2-0.html

with:
>> curl -s https://getcomposer.org/installer | php
>> php composer.phar create-project --dev --stability beta typo3/flow-base-distribution

The composer.json file shows the following content:
----------------------------------------------------------------------------------------
{
    "name": "typo3/flow-base-distribution",
    "description" : "TYPO3 Flow Base Distribution",
    "license": "LGPL-3.0+",
    "config": {
        "vendor-dir": "Packages/Libraries",
        "bin-dir": "bin"
    },
    "require": {
        "typo3/flow": "2.0.*",
        "typo3/welcome": "2.0.*",
        "doctrine/migrations": "@dev"
    },
    "require-dev": {
        "typo3/kickstart": "2.0.*",
        "typo3/buildessentials": "2.0.*",
        "mikey179/vfsstream": "1.1.*"
    },
    "scripts": {
        "post-update-cmd": "TYPO3\\Flow\\Composer\\InstallerScripts::postUpdateAndInstall",
        "post-install-cmd": "TYPO3\\Flow\\Composer\\InstallerScripts::postUpdateAndInstall"
    }
}
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