pykickstart 1.99.52 tightened up on wildcard imports, so some incorrect code in python-imgcreate doesn't slip through any more, and trying to create a live image crashes almost instantly:

File "/usr/lib/python2.7/site-packages/imgcreate/yuminst.py", line 139, in LiveCDYum
    def selectGroup(self, grp, include = pykickstart.parser.GROUP_DEFAULT):
AttributeError: 'module' object has no attribute 'GROUP_DEFAULT'

This is an automatic Alpha blocker, per criterion "All release-blocking images must boot in their supported configurations." - https://fedoraproject.org/wiki/Fedora_20_Alpha_Release_Criteria#Release-blocking_images_must_boot - (as it prevents two of the release-blocking images from being created at all) and the automatic blocker policy - https://fedoraproject.org/wiki/QA:SOP_blocker_bug_process#Automatic_blockers - "Bugs which entirely prevent the composition of one or more of the release-blocking images required to be built for a currently-pending (pre-)release".