* Remove Ubuntu 16.04 (Xenial Xerus) from CI.
* Removing PyOpenSSL backend from everywhere but openssl_pkcs12.
* Remove PyOpenSSL support from module_utils that's not needed for openssl_pkcs12.
* Add changelog fragment.
* Improve openssh_* tests.
* Use 2048 instead of 4096 bit keys in many places.
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* Parameterize default RSA key length for tests.
* Reduce default RSA key size to 1024.
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* Fix error.
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* Use variable more often.
* Use 2048 bits for RSA keys for certificates on RHEL8 and CentOS8.
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* Fix missing constant.
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* Print default key sizes.