Description of problem:
fedup fails unless --nogpgcheck is used
Version-Release number of selected component (if applicable):
0.90
How reproducible:
2-) fully update your f20 install (disable any no-fedora repositories)
3-) In root terminal:
yum update
yum install fedup
fedup --network 21 --product=workstation 
    NOTE: :"fedup tests may require the --nogpgcheck parameter until the signed .treeinfo file is available." 
Downloading failed: invalid data in .treeinfo: File contains no section headers,
file: .var.cache/system-upgrade/ ./treeinfo, line 1

fedup --network 21 --product=workstation --nogpgcheck
works

Additional info:
http://wiki.sugarlabs.org/go/File:Fedup_f20-f21.png