def get_package_versions(package_list):
    """
    Get packages information by inspecting __version__ attribute.

    Parameters:
    ----------
    package_list : list of str
        List of package names.

    Returns
    -------
    dict of module
        Version_info pairs.
    """
    module_versions = {}
    for module in package_list:
        try:
            module_versions[module] = __import__(module).__version__
        except ImportError:
            module_versions[module] = None
        except AttributeError:
            module_versions[module] = "unknown"
    return module_versions