Traceback (most recent call last):
File "/usr/bin/docktree", line 11, in <module>
sys.exit(main())
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 115, in main
Docktree(**vars(args)).draw_tree()
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 103, in draw_tree
draw_branch(prune(tree()))
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 79, in tree
return [(Image(img_dict, self.show_size), tree(img_dict['Id'])) for img_dict in children(root_id)]
File "/usr/lib/python2.7/site-packages/docktree/__init__.py", line 45, in __init__
self.tags = [t for t in img_dict['RepoTags'] if t != '<none>:<none>']
TypeError: 'NoneType' object is not iterable
