def run_command(command, env):
    """Run command in sub process.

    Runs the command in a sub process with the variables from `env`
    added in the current environment variables.

    Parameters
    ----------
    command: List[str]
        The command and it's parameters
    env: Dict
        The additional environment variables

    Returns
    -------
    int
        The return code of the command

    """
    # copy the current environment variables and add the vales from
    # `env`
    cmd_env = os.environ.copy()
    cmd_env.update(env)

    p = Popen(command,
              universal_newlines=True,
              bufsize=0,
              shell=False,
              env=cmd_env)
    _, _ = p.communicate()

    return p.returncode