"distribution was not found and is required by the application" when using pyinstaller with setuptools

Question

I am trying to make an executable from a setuptools distribution, I have the following structure:

TEST-DIST
├── app.spec
├── my_package
│   ├── __init__.py
│   ├── __main__.py
│   ├── script1.py
│   └── script2.py
└── setup.py

Setup.py:

from importlib.metadata import entry_points
import setuptools

setuptools.setup(
    name="testapp",
    version="0.0.1",
    author="Example Author",
    author_email="[email protected]",
    description="A small example package",
    url="https://github.com/pypa/sampleproject",
    project_urls={
        "Bug Tracker": "https://github.com/pypa/sampleproject/issues",
    },
    classifiers=[
        "Programming Language :: Python :: 3",
        "License :: OSI Approved :: MIT License",
        "Operating System :: OS Independent",
    ],
    entry_points={'console_scripts': ["mytestscript1=my_package.script1:main", "mytestscript2=my_package.script2:main"]},
    python_requires=">=3.6"
)

app.spec that uses this script to work with setuptools

block_cipher = None


def Entrypoint(dist, group, name, **kwargs):
    import pkg_resources

    # get toplevel packages of distribution from metadata
    def get_toplevel(dist):
        distribution = pkg_resources.get_distribution(dist)
        if distribution.has_metadata('top_level.txt'):
            return list(distribution.get_metadata('top_level.txt').split())
        else:
            return []

    kwargs.setdefault('hiddenimports', [])
    packages = []
    for distribution in kwargs['hiddenimports']:
        packages += get_toplevel(distribution)

    kwargs.setdefault('pathex', [])
    # get the entry point
    ep = pkg_resources.get_entry_info(dist, group, name)
    # insert path of the egg at the verify front of the search path
    kwargs['pathex'] = [ep.dist.location] + kwargs['pathex']
    # script name must not be a valid module name to avoid name clashes on import
    script_path = os.path.join(workpath, name + '-script.py')
    print("creating script for entry point", dist, group, name)
    with open(script_path, 'w') as fh:
        print("import", ep.module_name, file=fh)
        print("%s.%s()" % (ep.module_name, '.'.join(ep.attrs)), file=fh)
        for package in packages:
            print("import", package, file=fh)

    return Analysis(
        [script_path] + kwargs.get('scripts', []),
        **kwargs
    )

a = Entrypoint("testapp", 'console_scripts', 'mytestscript1')
pyz = PYZ(a.pure, a.zipped_data)

exe = EXE(pyz,
          a.scripts,
          a.binaries,
          a.zipfiles,
          a.datas,
          [],
          name='mytestscript1')

I first build the package using python3 -m build, Then I execute pyinstaller pyinstaller app.spec, Which results the following error:

27 INFO: PyInstaller: 4.10
27 INFO: Python: 3.8.10
34 INFO: Platform: Linux-5.10.60.1-microsoft-standard-WSL2-x86_64-with-glibc2.29
35 INFO: UPX is not available.
Traceback (most recent call last):
  File "/usr/local/bin/pyinstaller", line 8, in <module>
    sys.exit(run())
  File "/home/admin/.local/lib/python3.8/site-packages/PyInstaller/__main__.py", line 124, in run
    run_build(pyi_config, spec_file, **vars(args))
  File "/home/admin/.local/lib/python3.8/site-packages/PyInstaller/__main__.py", line 58, in run_build
    PyInstaller.building.build_main.main(pyi_config, spec_file, **kwargs)
  File "/home/admin/.local/lib/python3.8/site-packages/PyInstaller/building/build_main.py", line 803, in main
    build(specfile, distpath, workpath, clean_build)
  File "/home/admin/.local/lib/python3.8/site-packages/PyInstaller/building/build_main.py", line 725, in build
    exec(code, spec_namespace)
  File "app.spec", line 42, in <module>
    a = Entrypoint("testapp", 'console_scripts', 'mytestscript1', datas=[('testapp.egg-info/*','testapp.egg-info')])
  File "app.spec", line 25, in Entrypoint
    ep = pkg_resources.get_entry_info(dist, group, name)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 500, in get_entry_info
    return get_distribution(dist).get_entry_info(group, name)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 482, in get_distribution
    dist = get_provider(dist)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 358, in get_provider
    return working_set.find(moduleOrReq) or require(str(moduleOrReq))[0]
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 901, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 787, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'testapp' distribution was not found and is required by the application

The exception is invoked because pkg_resources.get_entry_info doesn't find my distribution when it is executed from pyinstaller, but when I run it from any normal script in the root it can be found without problems:

>>> import pkg_resources
>>> pkg_resources.get_entry_info("testapp", 'console_scripts', 'mytestscript1')
EntryPoint.parse('mytestscript1 = my_package.script1:main')

None of the solutions here helped!