def _validate_dependencies_met():
    """
    Verifies that PyOpenSSL's package-level dependencies have been met.
    Throws `ImportError` if they are not met.
    """
    from cryptography.x509.extensions import Extensions
    if getattr(Extensions, 'get_extension_for_class', None) is None:
        raise ImportError(
            "'cryptography' module missing required functionality.  Try upgrading to v1.3.4 or newer."
            )
    from OpenSSL.crypto import X509
    x509 = X509()
    if getattr(x509, '_x509', None) is None:
        raise ImportError(
            "'pyOpenSSL' module missing required functionality. Try upgrading to v0.14 or newer."
            )
