CalendarServer Error Domain:CalendarServerPromotion Code 1

After an upgrade to Server 4.1, I'm having problems with my calendar server crashing repeatedly:

5/22/15 1:41:02.216 PM com.apple.xpc.launchd[1]: (org.calendarserver.agent) Service only ran for 2 seconds. Pushing respawn out by 8 seconds.

5/22/15 1:41:13.173 PM com.apple.xpc.launchd[1]: (org.calendarserver.calendarserver[1054]) Service exited with abnormal code: 1

over and over again.

So I tried deleting Server.app, then re-installing it from the app store. When I do this, during the phase where it is setting up the server, I get a window which says

The following errors occurred while setting up your server.

'Preparing services - CalendarServer' Error Domain:CalendarServerPromotion Item:/Applications/Server.app/Contents/ServerRoot/usr/libexec/CalendarServerPro motion Code:1

I'm guessing I have a corrupt calendar database or something. Any way to fix this?