Detect "could not bring up vm 'builder_default'" and autoretry

Can any of the Python wizards take a bit of time off from the buildbot work and add a "small" patch? I'd guess it does not even need to rebuild the VM as this is not a NDK/Gradle update, the VM stays the same, just patch fdroidserver to retry.

This error is getting ridiculous, we have apps that fail to build cycle after cycle, not to mention whole cycles failing to build anything at all.

And it's not like "ok maybe tomorrow" since every next cycle might happen between 1 and 7 days, so ok we got 2 cycles this weekend...but...the previous one was on the 24.

Now, a "could not bring up" try finishes in about 6 minutes so even if it retries to build the same app it would do it for a maximum of 360 times... and it could fail every time or it might build eventually.

Not sure if it's easier to retry current or enqueue failed at the end, but any would do.

Thanks

/PS: Yes, I have an interest, I'd like to have Conversations 2.8.x (with Audio/Video support) build, the upstream dev even gave a head start of 2 days for F-Droid (the app is paid on Play FYI; but was free for the weekend as it it every year at this date).