_yaml.py: Do not insert into cache if retrieved from cache
Description
In _yaml.py::load()
ee were unconditionally inserting into the yaml cache anything we had
retrieved from the yaml cache. This had the side-effect of being expensive
on re-runs of commands where yaml hadn't changed.
Changes proposed in this merge request:
- Do not insert into the yaml cache unless we have had to parse the yaml this time around.
This merge request, when approved, will improve matters for: #466 (closed)