Desiutil 4

[weaverba137]

This PR demonstrates the transition to desiutil 4.0.0, the next major version. The planned changes are already documented in the changes.rst file.

This major version is more about removing code than adding it, so the changes only took a couple of hours to implement, might as well get a draft.

We can discuss exactly when to merge this, but definitely this should not get in the way of the Matterhorn production.

• Closes desiutil.setup may be incompatible with recent versions of setuptools #198
• Closes Style and API change in ebv() #213

[coveralls]

coverage: 80.852% (+4.7%) from 76.18% — desiutil-4 into main

[weaverba137]

@sbailey, some additional details about the PR:

1. Top-level setup.py is no longer needed and is removed.
2. desiutil.census is removed along with its test suite and configuration file. This module has long been replaced by the NERSC metadata reports and the software that interprets them is in the decamUtil package.
3. update_iers_frozen, iers_frozen.ecsv and the update_iers() function are removed. The IERS files are now copies of Astropy's astropy-iers-data files. The format of the iers_frozen.ecsv file is no longer compatible with current versions of Astropy.
4. flake8 is added to the code style checks in "allowed failure" mode. flake8 does some basic "linting" like finding unused variable assignments in addition to code style checks.
5. flake8 noticed that there were two copies of the method test_plot_sky_binned in test_plots.py, as well as an apparent typo in an f"" string.
6. desiutil.dust._main() is renamed to desiutil.dust.main() for better compatibility with the test coverage system.