If you were trying to pull the latest source code on your Raspberry Pi for donkeycar, and get the following error, then probably your clock is off (and I guess some nonce is failing). This can happen if your pi had been powered off for a while (as in my case), and it’s clock is off (clock drift is a real thing) :).
fatal: unable to access 'https://github.com/wroscoe/donkey/': server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
To fix this, the following commands works. It seems the Raspberry Pi 3, by default has NTP disabled and this would enable it. I also had to check the result status with the second command, and force it with the third one.
sudo timedatectl set-ntp True timedatectl status sudo timedatectl set-local-rtc true
And that should do it; you might need to reboot the pi just to get it back on and then you should be able to pull the code off git and deploy your autonomous car.