The error is not necessarily due to a client certificate engine. For
example, the `privateKeyEngine` option might just as well cause this
error and is independent of the client certificate.
Also mention that this is likely due to a compile-time option of OpenSSL
itself and not due to any particular engine.
PR-URL: https://github.com/nodejs/node/pull/47976
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Tobias Nießen
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