You should get something like SHA1 Fingerprint=9E:FD:0A:7B:C0:40:3D:A9:CF:BD:FE:DA:5E:D3:A8:EB:04:DB:2D:33 take the hexidecimal value and use it the next step
Add the following to your hgrc file
[hostfingerprints]
<FQDN from step 1> = <HEXVALUE from step 2>
Disable SSL verification
It goes without saying the this is not a very good idea, but if all else fails this will get mercrial to talk to a self signed https server