It's not bad form to edit the answer even after it's accepted if the edits clarify it and there is a viewable history if necessary. I too encountered this error (on OS X 10.9) and fortunately hadn't removed the deactivated previous libgpg-error, so just your original port -f deactivate libgpg-error @1.24_0 followed by port -f activate libgpg-error @1.24_0 saved me from a world of grief. The only thing we need to remember is to reactivate the new one when GPG 2.1.16 is available as a port. Good work, BTW.