Snippet from {{{/usr/bin/fedora-packager-setup}}}:
{{{
115 if not os.path.islink(upload_ca_cert):
116 print 'Linking: ~/.fedora-server-ca.cert to ~/.fedora-upload-ca.cert'
117 os.unlink(upload_ca_cert)
118 os.symlink(server_ca_cert, upload_ca_cert)
}}}

Line 117 fails if {{{.fedora-upload-ca.cert}}} doesn't exist; {{{os.path.islink}}} returns {{{False}}}, but there's nothing to unlink.

{{{.fedora-upload-ca.cert}}} is probably going to be a file, if it already exists; so replacing line 117 with this should be OK (and works for me):

{{{
if os.path.isfile(upload_ca_cert):
os.unlink(upload_ca_cert)
}}}

A workaround is to do

{{{
touch .fedora-upload-ca.cert
}}}

before running {{{fedora-packager-setup}}}.