Tests fail when run via "python -m pytest"

Could you please make the tests not rely on specific argv[0]? We're running tests on Gentoo via python -m pytest as that guarantees that the correct Python version/environment will be used, and this means argv[0] is __main__ rather than pytest.
========================================================= test session starts =========================================================
platform linux -- Python 3.10.10, pytest-7.2.1, pluggy-1.0.0
cachedir: .tox/py310/.pytest_cache
rootdir: /tmp/argh
plugins: cov-4.0.0
collected 102 items                                                                                                                   

tests/test_assembling.py ...................                                                                                    [ 18%]
tests/test_completion.py ...                                                                                                    [ 21%]
tests/test_decorators.py ......                                                                                                 [ 27%]
tests/test_dispatching.py ...                                                                                                   [ 30%]
tests/test_integration.py .......xxx......................................FFF                                                   [ 80%]
tests/test_interaction.py .....                                                                                                 [ 85%]
tests/test_regressions.py .......                                                                                               [ 92%]
tests/test_utils.py ........                                                                                                    [100%]

============================================================== FAILURES ===============================================================
___________________________________________________ test_add_commands_no_overrides ____________________________________________________

    def test_add_commands_no_overrides():
        def first_func(foo=123):
            """Owl stretching time"""
            pass

        def second_func():
            pass

        p = argh.ArghParser()
        p.add_commands(
            [first_func, second_func],
        )

        with iocapture.capture() as captured:
            run(p, "--help", exit=True)
>           assert (
                captured.stdout
                == unindent(
                    f"""
                usage: pytest [-h] {{first-func,second-func}} ...

                positional arguments:
                  {{first-func,second-func}}
                    first-func          Owl stretching time
                    second-func

                {HELP_OPTIONS_LABEL}:
                  -h, --help            show this help message and exit
                """
                )[1:]
            )
E           AssertionError: assert 'usage: __mai...ge and exit\n' == 'usage: pytes...ge and exit\n'
E             - usage: pytest [-h] {first-func,second-func} ...
E             ?          ----
E             + usage: __main__.py [-h] {first-func,second-func} ...
E             ?        +++++++++
E               
E               positional arguments:
E                 {first-func,second-func}...
E             
E             ...Full output truncated (6 lines hidden), use '-vv' to show

tests/test_integration.py:807: AssertionError
________________________________________________ test_add_commands_namespace_overrides ________________________________________________

    def test_add_commands_namespace_overrides():
        """
        When `namespace_kwargs` is passed to `add_commands()`, its members override
        whatever was specified on function level.
        """

        def first_func(foo=123):
            """Owl stretching time"""
            pass

        def second_func():
            pass

        p = argh.ArghParser()
        p.add_commands(
            [first_func, second_func],
            namespace="ns",
            namespace_kwargs={
                "help": "namespace help override",
                "description": "namespace description override",
            },
        )

        with iocapture.capture() as captured:
            run(p, "--help", exit=True)
>           assert (
                captured.stdout
                == unindent(
                    f"""
                usage: pytest [-h] {{ns}} ...

                positional arguments:
                  {{ns}}
                    ns

                {HELP_OPTIONS_LABEL}:
                  -h, --help  show this help message and exit
                """
                )[1:]
            )
E           AssertionError: assert 'usage: __mai...ge and exit\n' == 'usage: pytes...ge and exit\n'
E             - usage: pytest [-h] {ns} ...
E             ?          ----
E             + usage: __main__.py [-h] {ns} ...
E             ?        +++++++++
E               
E               positional arguments:
E                 {ns}...
E             
E             ...Full output truncated (5 lines hidden), use '-vv' to show

tests/test_integration.py:867: AssertionError
__________________________________________________ test_add_commands_func_overrides ___________________________________________________

    def test_add_commands_func_overrides():
        """
        When `func_kwargs` is passed to `add_commands()`, its members override
        whatever was specified on function level.
        """

        def first_func(foo=123):
            """Owl stretching time"""
            pass

        def second_func():
            pass

        p = argh.ArghParser()
        p.add_commands(
            [first_func, second_func],
            func_kwargs={
                "help": "func help override",
                "description": "func description override",
            },
        )

        with iocapture.capture() as captured:
            run(p, "--help", exit=True)
>           assert (
                captured.stdout
                == unindent(
                    f"""
                usage: pytest [-h] {{first-func,second-func}} ...

                positional arguments:
                  {{first-func,second-func}}
                    first-func          func help override
                    second-func         func help override

                {HELP_OPTIONS_LABEL}:
                  -h, --help            show this help message and exit
                """
                )[1:]
            )
E           AssertionError: assert 'usage: __mai...ge and exit\n' == 'usage: pytes...ge and exit\n'
E             - usage: pytest [-h] {first-func,second-func} ...
E             ?          ----
E             + usage: __main__.py [-h] {first-func,second-func} ...
E             ?        +++++++++
E               
E               positional arguments:
E                 {first-func,second-func}...
E             
E             ...Full output truncated (6 lines hidden), use '-vv' to show

tests/test_integration.py:947: AssertionError
======================================================= short test summary info =======================================================
FAILED tests/test_integration.py::test_add_commands_no_overrides - AssertionError: assert 'usage: __mai...ge and exit\n' == 'usage: pytes...ge and exit\n'
FAILED tests/test_integration.py::test_add_commands_namespace_overrides - AssertionError: assert 'usage: __mai...ge and exit\n' == 'usage: pytes...ge and exit\n'
FAILED tests/test_integration.py::test_add_commands_func_overrides - AssertionError: assert 'usage: __mai...ge and exit\n' == 'usage: pytes...ge and exit\n'
=============================================== 3 failed, 96 passed, 3 xfailed in 0.59s ===============================================
neithere / argh

Tests fail when run via "python -m pytest" #170
