out-of-the-blue codesigning error

[Mike Kerner]

An app that I have been using and deploying to my team for months is now
failing to build with "codesigning failed with aps-environment
development"

I checked the certs in keychain and in xcode and at apple's developer
portal, and nothing seems to be expired or otherwise out of the ordinary.
So any ideas on what to try next?

-- 
On the first day, God created the heavens and the Earth
On the second day, God created the oceans.
On the third day, God put the animals on hold for a few hours,
   and did a little diving.
And God said, "This is good."