What genes are required to make E. coli photosynthetic?
I think the crux of the answer is only hinted at in WYSIWYG's answer. The crux of photosynthesis is partitioning coupled reactions.

Photosynthesizing plant cells have sub-cellular structures called chloroplasts; their membranes are especially important for the compartmentalization of different functions and chemical processes for the entirety of photosynthesis to even be possible. Partitioning is difficult to achieve in E. coli, and that to me seems a necessity for achieving true heterologous, truly ectopic photosynthesis... Even photosynthesizing cyanobacteria (photosynthesizing prokaryotes) possess thylakoids, membrane-bound compartments where the magic happens. Photosynthesis though can certainly proceed and be made more efficient in single cells (example).
That leaves us with a simple answer: engineering E. coli with thylakoid-like structures is not really practicable. Why not simple use cyanobacteria instead?
Further reading: review on single cell photosynthesis in single cells.