Return the path to the activate binary

def _get_env_activate(bin_env):
    '''
    Return the path to the activate binary
    '''
    if not bin_env:
        raise CommandNotFoundError('Could not find a `activate` binary')

    if os.path.isdir(bin_env):
        if salt.utils.platform.is_windows():
            activate_bin = os.path.join(bin_env, 'Scripts', 'activate.bat')
        else:
            activate_bin = os.path.join(bin_env, 'bin', 'activate')
        if os.path.isfile(activate_bin):
            return activate_bin
    raise CommandNotFoundError('Could not find a `activate` binary')