Competing tag/context config for image provides inconsistent result

[thibaudcolas]

Issue Summary

Initially reported by @tombola, sounds similar to something I’ve seen other reports of but we need a detailed example to reproduce.

If an image tag is assigned to a target value in the YAML, then an image: True is required in the context YAML in order for the template to test if the image exists. If an image tag is not assigned to a target value, then image: True in the context config breaks the template. Encountered recently, not exhaustively tested. Linked to helen's error message item above.

Steps to Reproduce

TBD

[thibaudcolas]

Fixed in #141 :)