Issue with RabbitMQ 3.8.5, trust store, and TLS authentication

[lukebakken]

Repo with artifacts - https://github.com/lukebakken/tls-auth-cert-store-GHeD-CRU5lk

Reported via this rabbitmq-users discussion

To reproduce using 3.8.5:

• Enable the rabbitmq_trust_store and rabbitmq_auth_mechanism_ssl plugins.
• Start RabbitMQ using this configuration file. Note that the trust store is configured, but no cacertfile is set.
• The ranch listener will not start correctly:

2020-07-08 16:15:32.686 [error] <0.694.0> Failed to start Ranch listener {acceptor,{0,0,0,0,0,0,0,0},5671} in ranch_ssl:listen([{cacerts,'...'},{key,'...'},{cert,'...'},{ip,{0,0,0,0,0,0,0,0}},{port,5671},inet6,{backlog,128},{nodelay,true},{linger,{true,0}},{exit_on_close,false},{versions,['tlsv1.2','tlsv1.1',tlsv1]},{keyfile,"/home/lbakken/issues/rabbitmq-users/tls-auth-cert-store-GHeD-CRU5lk/certs/server_key.pem"},{certfile,"/home/lbakken/issues/rabbitmq-users/tls-auth-cert-store-GHeD-CRU5lk/certs/server_certificate.pem"},{fail_if_no_peer_cert,true},{verify,verify_peer}]) for reason {options,{cacertfile,[]}} (unknown POSIX error)