Improve error message when someone tries to cook a group with a different version per flavor
Improve error message when someone tries to cook a group with a different version per flavor

Usually triggered by a recipe like this:
class MyGroup(GroupRecipe):
    name = 'group-mygroup'
    version = time.strftime('%Y%m%d%H%M')

Then when the group load takes longer than a minute or otherwise
straddles a minute boundary, each flavor ends up with a unique source
version.

fedora-conary/conary,fedora-conary/conary,fedora-conary/conary,fedora-conary/conary,fedora-conary/conary