Flask + Apache = Internal Server Error 500 when configured from the flask site. Where is the mistake?

Question

Apache HTTP Server

I do everything like in this video https://www.youtube.com/watch?v=yMbiW45O_RA&t=13s , but the result is always one Internal Server Error. I looked through the documentation of the official flask site, everything matches there, I did the same work earlier on a virtual machine (now I work on the installed OS) - everything worked. I even found this machine and the necessary files. There is no difference in what I did then and what I am doing now, except for what worked then (and works, I checked), but not now.
I've been fiddling with this for a long time and can't figure out what's wrong. Help, here is the code:

init.py

activate_this_file = "/var/www/site/venv/bin/activate_this_file.py"
with open(activate_this_file) as _file:
    exec(_file.read(), dict(__file__ = activate_this_file))

from flask import Flask

app = Flask(__name__)

@app.route("/")
def hello_world():
    return "<p>Hello, World!</p>"
@app.route("/done")
def do():
    return "RRRRRRR"

app.wsgi

#!/usr/bin/env python
import sys
sys.path.insert(0, '/var/www/site/')

from init import app as application

000-default.conf

<VirtualHost *:80>
  # The ServerName directive sets the request scheme, hostname and port that
  # the server uses to identify itself. This is used when creating
  # redirection URLs. In the context of virtual hosts, the ServerName
  # specifies what hostname must appear in the request's Host: header to
  # match this virtual host. For the default virtual host (this file) this
  # value is not decisive as it is used as a last resort host regardless.
  # However, you must set it for any further virtual host explicitly.
  #ServerName www.example.com

  #ServerAdmin [email protected]
  #DocumentRoot /var/www/html

  WSGIScriptAlias / /var/www/site/app.wsgi
  <Directory /var/www/site>
    Order allow,deny
    Allow from all
  </Directory>

  # Available loglevels: trace8, ..., trace1, debug, info, notice, warn,
  # error, crit, alert, emerg.
  # It is also possible to configure the loglevel for particular
  # modules, e.g.
  #LogLevel info ssl:warn

  ErrorLog ${APACHE_LOG_DIR}/error.log
  CustomLog ${APACHE_LOG_DIR}/access.log combined

  # For most configuration files from conf-available/, which are
  # enabled or disabled at a global level, it is possible to
  # include a line for only one particular virtual host. For example the
  # following line enables the CGI configuration for this host only
  # after it has been globally disabled with "a2disconf".
  #Include conf-available/serve-cgi-bin.conf
</VirtualHost>

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

Answer 1

An error in the logs, of course.
PS When you do everything according to the video, but you get an error, you should think about the quality of the video.

Answer 2

if the configs are correct - does the Web server have rights to the files in the folder you point to?
well, I hope the web server with the new config restarted normally and without errors?