Work with endpoints that support HTTP macaroons but not for COPY

It appears that, while DPM endpoints support Macaroons for authorization, attempts to use a Macaroon to initiate a HTTP COPY result in a response that requests a credential.  Here's what I get as a response from DPM to a HTTP COPY request authorized with a Macaroon:

DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < HTTP/1.1 302 Found
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < Date: Fri, 27 Jul 2018 14:44:05 GMT
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < Server: Apache/2.2.15 (Red Hat)
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < X-Delegate-To: /gridsite-delegation
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < Location: /srv/dpm/volume/dteam/2018-07-27/bigfile.3.5810.1532702645?sfn=%2Fdpm%2Fcern.ch%2Fhome%2Fdteam%2Fbigfile.3&token=BX2Sl6IWo%2ByH9PAqqvT5ftAinu4%3D%401532703645%401&copyRedirected=1
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < Vary: Accept-Encoding
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < Content-Length: 460
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < Keep-Alive: timeout=15, max=100
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < Connection: Keep-Alive
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: < Content-Type: text/html; charset=iso-8859-1
DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Davix: <

I think that it is requesting a delegation back.  GFAL2 doesn't know what to do; in the FTS log, I see:

DEBUG Fri, 27 Jul 2018 16:44:06 +0200; Copy failed with mode 3rd pull, will retry with the next available mode: [davix2gliberr] copy No callback set for getting credentials. Can not delegate

In this case, should we just proceed with a gridsite delegation?