The tests actually require wheel

When wheel is not installed, several tests error like this:

    distutils.errors.DistutilsModuleError: invalid command 'bdist_wheel'
    ...
    SystemExit: error: invalid command 'bdist_wheel'

Or like this:

    ERROR Missing dependencies:
    	wheel

When the tests are executed in a virtualenv, wheel is implicitly installed,
which is why this have never happened on the CI.

List of tests that error:

     ERROR tests/tox_env/python/virtual_env/package/test_package_cmd_builder.py::test_tox_install_pkg_wheel
     ERROR tests/tox_env/python/virtual_env/package/test_package_cmd_builder.py::test_tox_install_pkg_sdist
     ERROR tests/tox_env/python/virtual_env/package/test_package_cmd_builder.py::test_install_pkg_via[p]
     ERROR tests/tox_env/python/virtual_env/package/test_package_cmd_builder.py::test_install_pkg_via[le]
     ERROR tests/tox_env/python/virtual_env/package/test_python_package_util.py::test_load_dependency_no_extra
     ERROR tests/tox_env/python/virtual_env/package/test_python_package_util.py::test_load_dependency_many_extra

Version 0.38.4 is required as this is the current version
and this is the way tox specifies the test dependencies.

docs/changelog/2843.bugfix.rst

@@ -0,0 +1 @@
+Explicitly list ``wheel`` as requirement for the tests, as some of the tests error without it.

pyproject.toml

@@ -60,6 +60,7 @@ optional-dependencies.testing = [
   "pytest-mock>=3.10",
   "pytest-xdist>=3.1",
   "re-assert>=1.1",
+  "wheel>=0.38.4",
   "time-machine>=2.8.2; implementation_name != \"pypy\"",
 ]
 scripts.tox = "tox.run:run"