Deploying rubin-env 0.6.0

On Tuesday, 2021-05-11, we updated our build infrastructure to use version 0.6.0 of the rubin-env conda-forge metapackage. The w_2021_20 weekly will be the first tagged release to incorporate this change.

This new environment adds the alembic package as requested in RFC-779. In addition, click is pinned to avoid a major version change, and sqlalchemy is allowed to float to versions 1.4.x.

rubin-env 0.6.0 should be used with all Science Pipelines code on or after w_2021_20. We believe it can be used successfully with all Science Pipelines code on or after w_2021_05. For older code, please use rubin-env 0.1.5.