Unclear error message if run on CMF which has been cloned without git LFS.

[andrewphilipsmith]

Expected behaviour

A useful, informative and actionable error message is returned.

Actual behaviour

An opaque error message is returned:
Object: CreateObject cannot open map document

How to reproduce

1. Download the default cmf as a zip
2. Ammend the event_description.json
3. Add some data as required to 2_Active_Data
4. Run

mapchef maps --build /path/to/event_description.json

[simran212530]

@andrewphilipsmith Sir can I work on this issue?