WIP: Initial creation of defects emmet builder

[dbroberg]

Initial working version of defects template.

[dwinston]

Thanks for sharing this, @dbroberg.

Builder.process_item must not do I/O -- that means no MPRester calls (in your case, process_item calls get_bulk_gap_data, which calls MPRester ). In fact, there should be no (explicit) use of MPRester in an emmet builder -- you should connect directly to materials and bandstructures stores just like you connect to a tasks store. Builder.get_items should do all data fetching and pass items to process_item for "offline" processing prior to updating target stores in update_targets.

You can define, for testing purposes, simple stores that call MPRester under the hood -- as long as the builder uses only Store interfaces to fetch structures and bandstructures.

We will also need at least a sanity-check test (see test files for other builders) in order to merge this.

[shyamd]

I'm taking over this builder as @dbroberg is leaving us :(