mdwrite wants to use the "metadata" keychain.

A couple of days ago, my Mac started asking:

mdwrite wants to use the "metadata" keychain.

Please enter the keychain password.

Password: [ ]

Over and over and over again. I don't know what the password is. If I hit Cancel a bunch of times the dialog will go away... for a bit.

I found posts from 2011(!) with no resolution to this same problem which is a little alarming. I decided to post again to see if anyone has any more insight.

I use this computer for work. I need it to work well!