add PYTHONPATH for extension's install.py

    return [x for x in args if x != name], name in args

def run(command, desc=None, errdesc=None):

def run(command, desc=None, errdesc=None, custom_env=None):

    if desc is not None:

        print(desc)

    result = subprocess.run(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)

    result = subprocess.run(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True, env=os.environ if custom_env is None else custom_env)

    if result.returncode != 0:

            continue

        try:

            print(run(f'"{python}" "{path_installer}"', errdesc=f"Error running install.py for extension {dirname_extension}"))

            env = os.environ.copy()

            env['PYTHONPATH'] = os.path.abspath(".")

            print(run(f'"{python}" "{path_installer}"', errdesc=f"Error running install.py for extension {dirname_extension}", custom_env=env))

        except Exception as e:

            print(e, file=sys.stderr)