Flask: Unicode decode error in empty testing file

Question

I only open a logging file:

logging.basicConfig(level=logging.DEBUG,
                    filename='app.log',
                    filemode='w', encoding='utf-8')

and a html file (Flask):

site = Template(render_template('base.html',  list_of_active_tasks=active_tasks,
                                    list_of_completed_tasks=completed_tasks, checker=checker,
                                    type_of_list=type_of_list))

Every single file have utf-8 encoding, but that is what i get when launching a testing file:

Traceback (most recent call last):
  File "C:\Program Files\JetBrains\PyCharm Community Edition 2021.3.2\plugins\python-ce\helpers\pycharm\_jb_pytest_runner.py", line 51, in <module>
    sys.exit(pytest.main(args, plugins_to_load + [Plugin]))
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\__init__.py", line 146, in main
    config = _prepareconfig(args, plugins)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\__init__.py", line 325, in _prepareconfig
    config = pluginmanager.hook.pytest_cmdline_parse(
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\pluggy\_hooks.py", line 265, in __call__
    return self._hookexec(self.name, self.get_hookimpls(), kwargs, firstresult)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\pluggy\_manager.py", line 80, in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\pluggy\_callers.py", line 55, in _multicall
    gen.send(outcome)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\helpconfig.py", line 102, in pytest_cmdline_parse
    config: Config = outcome.get_result()
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\pluggy\_result.py", line 60, in get_result
    raise ex[1].with_traceback(ex[2])
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\pluggy\_callers.py", line 39, in _multicall
    res = hook_impl.function(*args)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\__init__.py", line 1013, in pytest_cmdline_parse
    self.parse(args)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\__init__.py", line 1301, in parse
    self._preparse(args, addopts=addopts)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\__init__.py", line 1169, in _preparse
    self._initini(args)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\__init__.py", line 1088, in _initini
    rootpath, inipath, inicfg = determine_setup(
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\findpaths.py", line 186, in determine_setup
    rootdir, inipath, inicfg = locate_config([ancestor])
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\findpaths.py", line 108, in locate_config
    ini_config = load_config_dict_from_file(p)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\findpaths.py", line 56, in load_config_dict_from_file
    iniconfig = _parse_ini_config(filepath)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\_pytest\config\findpaths.py", line 30, in _parse_ini_config
    return iniconfig.IniConfig(str(path))
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\iniconfig\__init__.py", line 54, in __init__
    tokens = self._parse(iter(f))
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\site-packages\iniconfig\__init__.py", line 82, in _parse
    for lineno, line in enumerate(line_iter):
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\encodings\cp1251.py", line 23, in decode
    return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: 'charmap' codec can't decode byte 0x98 in position 234: character maps to <undefined>

Process finished with exit code 1

Empty suite

Empty suite

Moreover, my app is working without any issues, but test does not work. How can i fix it?