Running a Telegram bot behind a proxy server that inspects traffic results in an SSL certificate error. Setting REQUESTS_CA_BUNDLE or SSL_CERT_FILE does not work because python-telegram-bot uses certifi which respects neither of the environment variables.

My feature request is that a parameter "use system certificates" or an argument for the certificates file path on the Updater (and probably on Bot as well because that class actually instantiates the Request class) gets added.

It could also be an argument on the Request class that we can set by passing the request_kwargs to the Updater or a Request object directly to the Bot.