I’ve been talking to my teammate about this certificate error. Could not load host key: /etc/ssh/hostkeys/ssh_host_dsa_key is apparently harmless. At least it should not cause that certificate problem. The host keys are generated at first boot, the epoch timestamp could happen if the device defaults to epoch time and SSH started before time sync was complete.
Since the date command returns the correct date now, could you try running pip command once more now?
Let’s see if it fails again.