Check with yamllint the yaml syntaxes
    Looking for duplicate keys.

def validate_yaml(yaml_in, yaml_fn):
    """Check with yamllint the yaml syntaxes
    Looking for duplicate keys."""
    try:
        import yamllint.linter as linter
        from yamllint.config import YamlLintConfig
    except ImportError:
        return
    conf = """{"extends": "relaxed",
               "rules": {"trailing-spaces": {"level": "warning"},
                         "new-lines": {"level": "warning"},
                         "new-line-at-end-of-file": {"level": "warning"}}}"""
    if utils.file_exists(yaml_in):
        with open(yaml_in) as in_handle:
            yaml_in = in_handle.read()
    out = linter.run(yaml_in, YamlLintConfig(conf))

    for problem in out:
        msg = '%(fn)s:%(line)s:%(col)s: [%(level)s] %(msg)s' % {'fn': yaml_fn,
                                                                'line': problem.line,
                                                                'col': problem.column,
                                                                'level': problem.level,
                                                                'msg': problem.message}
        if problem.level == "error":
            raise ValueError(msg)