python-whey's test suite hard-codes the name of the .pth file that
editables generates for editable installs. editables 0.6 renamed it
from <project>.pth to _editable_impl_<project>.pth, so with
python3-editables 0.6 installed the build fails (7 failed, 227 passed,
74 skipped):

  FAILED tests/test_build.py::test_build_editable[0.3-COMPLETE_A]
  FAILED tests/test_build.py::test_build_editable[0.3-COMPLETE_B]
  FAILED tests/test_build.py::test_build_editable[0.3-LONG_REQUIREMENTS]
  FAILED tests/test_build.py::test_build_editable_namespace
  FAILED tests/test_builder_methods.py::test_create_editables_files[0.3]
  FAILED tests/test_pep517_backend.py::test_build_editable[0.3-COMPLETE_A]
  FAILED tests/test_pep517_backend.py::test_build_editable[0.3-COMPLETE_B]

Each one is a FileNotFoundError for whey.pth (default_values.pth in the
namespace test). Because the package uses Testsuite:
autopkgtest-pkg-pybuild, its autopkgtest will fail the same way.

whey itself works fine with 0.6 (it writes _editable_impl_whey.pth);
only the expected file names in the tests are out of date.

python-editables 0.6-1 is ready on Salsa but not uploaded yet:
https://salsa.debian.org/python-team/packages/python-editables
I'm filing this first so it's tracked before that upload. Once 0.6 is
in unstable I'll raise the severity to serious.

Upstream fixed the tests in c29cf907d3 ("Bump editables to 0.6"),
which is not in a release yet:
https://github.com/repo-helper/whey/commit/c29cf907d3ee95080c8f4a60c81a8a584aa0a51b

That commit doesn't apply to 0.1.1, so the attached patch makes the
same change: it renames the expected files and keeps the wheel
contents in the order whey writes them. With it applied, 0.1.1-6
builds in a sid chroot against python3-editables 0.6-1: 234 passed,
74 skipped (the same counts as with 0.5-3 today).

The patched tests only pass with editables 0.6, so the patch can't go
in before the editables upload.