Description of problem:
Running atomic verify results in the error:
TypeError: argument of type 'NoneType' is not iterable


Version-Release number of selected component (if applicable):
atomic 1:1.12.1-4.el7
skopeo 1:0.1.14-0.5.el7

How reproducible:
100%

Steps to Reproduce:
1. as root, run 
atomic --debug verify -v --no-validate docker.io/library/busybox:latest

Actual results:
http://pastebin.test.redhat.com/412848
# atomic --debug verify -v --no-validate docker.io/library/busybox:latest
argument of type 'NoneType' is not iterable
Traceback (most recent call last):
  File "/bin/atomic", line 186, in <module>
    sys.exit(_func())
  File "/usr/lib/python2.7/site-packages/Atomic/verify.py", line 121, in verify
    layers = fix_layers(self.get_layers())
  File "/usr/lib/python2.7/site-packages/Atomic/atomic.py", line 415, in get_layers
    layer = self._get_layer(self.image)
  File "/usr/lib/python2.7/site-packages/Atomic/atomic.py", line 410, in _get_layer
    "Version": version, "Tag": find_repo_tag(self.d, image['Id'], self.image),
  File "/usr/lib/python2.7/site-packages/Atomic/atomic.py", line 33, in find_repo_tag
    repo_tag = image_in_repotags(image_name, image['RepoTags'])
  File "/usr/lib/python2.7/site-packages/Atomic/atomic.py", line 23, in image_in_repotags
    if image_name in repotags:
TypeError: argument of type 'NoneType' is not iterable


Expected results:


Additional info: