The Python 3.7.13 version used in the containers are using OpenSSL 1.0.2g 1 Mar 2016

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import ssl
[...]
    def configure(self):
        self.output.info(ssl.OPENSSL_VERSION)

OpenSSL added TLS 1.3 support in 1.1.1+

Hence, Conan can not download sources from servers that only support TLS 1.3.

This was a problem in conan-io/conan-center-index#23234

Right now, this might be the exception, but this will become a bigger problem over time. I am opening this issue to raise some awareness about this problem.