flit_core 4 bugfix

Building with flit_core 4 fails with:

* Building wheel...
Traceback (most recent call last):
  File "/usr/pkg/lib/python3.14/site-packages/pyproject_hooks/_in_process/_in_process.py", line 389, in <module>
    main()
    ~~~~^^
  File "/usr/pkg/lib/python3.14/site-packages/pyproject_hooks/_in_process/_in_process.py", line 373, in main
    json_out["return_val"] = hook(**hook_input["kwargs"])
                             ~~~~^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/pkg/lib/python3.14/site-packages/pyproject_hooks/_in_process/_in_process.py", line 280, in build_wheel
    return _build_backend().build_wheel(
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        wheel_directory, config_settings, metadata_directory
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/usr/pkg/lib/python3.14/site-packages/flit_core/buildapi.py", line 74, in build_wheel
    info = make_wheel_in(pyproj_toml, Path(wheel_directory))
  File "/usr/pkg/lib/python3.14/site-packages/flit_core/wheel.py", line 222, in make_wheel_in
    wb = WheelBuilder.from_ini_path(ini_path, fp)
  File "/usr/pkg/lib/python3.14/site-packages/flit_core/wheel.py", line 86, in from_ini_path
    ini_info = read_flit_config(ini_path)
  File "/usr/pkg/lib/python3.14/site-packages/flit_core/config.py", line 75, in read_flit_config
    return prep_toml_config(d, path)
  File "/usr/pkg/lib/python3.14/site-packages/flit_core/config.py", line 106, in prep_toml_config
    loaded_cfg = read_pep621_metadata(d['project'], path)
  File "/usr/pkg/lib/python3.14/site-packages/flit_core/config.py", line 385, in read_pep621_metadata
    raise ConfigError(
        "Unrecognised key(s) in [project] table: " + ', '.join(unexpected_keys)
    )
flit_core.config.ConfigError: Unrecognised key(s) in [project] table: author

TIP pass --env-dir and --sdist-extract-dir to keep the build environment and sources, then see https://build.pypa.io/en/stable/how-to/troubleshooting.html#debug-a-failed-build for help debugging a failed build
ERROR Backend subprocess exited when trying to invoke build_wheel

The fix is easy:

--- pyproject.toml.orig 2026-08-12 22:19:08.364157397 +0000
+++ pyproject.toml
@@ -4,7 +4,7 @@ license = { file = "LICENSE.txt" }
 description = "A toolbar overlay for debugging Flask applications."
 readme = "README.md"
 license = { file = "LICENSE.txt" }
-author = [{ name = "Michael van Tellingen" }]
+authors = [{ name = "Michael van Tellingen" }]
 maintainers = [{ name = "Pallets Ecosystem", email = "contact@palletsprojects.com" }]
 classifiers = [
     "Development Status :: 4 - Beta",

Open pyproject.toml and inspect the [project] metadata used by flit_core 4. Correct the singular author metadata key, then rerun the wheel build that currently fails and confirm the package builds successfully without the ConfigError.