This may not be practical, but it seems if would be convenient if pagure kept your ssh key in sync with FAS.

So there are two issues in here,

• pagure should be retrieving you ssh key from FAS via ipsilon, this is
  something that worked at one point and for some reasons does not these days,
  I'll ping @puiterwijk to know if he could have a quick look at it.
  The idea being that if you do not have a ssh key set in pagure, it will use
  the one in FAS

• Once you do have a ssh key in pagure (from FAS or otherwise) pagure will
  simply ignore the ssh key returned by ipsilon upon log in.
  The idea is that pagure has no way to know if the ssh key changed in FAS or if
  you prefer to use to different ssh keys (in for Fedora the other for pagure),
  especially considering that pagure supports having multiple ssh keys which
  could be used for different use-case

So the "keep in sync with FAS" should and will be only true if you do not have a
ssh key already set-up in pagure, otherwise you will have to remember to change
the key in both places.

Fixed in ipsilon at: https://pagure.io/ipsilon/pull-request/100

I'm going to close this as fixed.