SQLAlchemy: table version already exists. pgAdmin4 fails on Linux Mint 20 and 20.1

*I already found the solution, I just want to share it in case someone has the same problem.* ### Situation ### Install pgAdmin4 version 4.30 on Linux Mint 20 (Ulyana) and Linux Mint 20.1 (Ulyssa) inside virtualenv. The bulk of pgAdmin4 is a Python web application written using the Flask framework. Therefore, it is an ideal candidate to be implemented in a Python virtualenv as indicated in: [How to Install PostgreSQL with pgAdmin4 on Linux Mint 20](https://www.tecmint.com/install-postgresql-with-pgadmin4-on-linux-mint/) And, [Installing pgAdmin 4 on Linux Mint 20 (ulyana)](https://medium.com/@ogunyemijeremiah/installing-pgadmin-4-on-linux-mint-20-ulyana-741b941479c9) And in Spanish, [Cómo instalar PostgreSQL con pgAdmin4 en Linux Mint 20](https://es.linux-console.net/?p=2457) ### Error ### After finishing the process, when trying to run pgAdmin4 for the **first time**, the following error appears:

Traceback (most recent call last):
  File "venv/lib/python3.8/site-packages/pgadmin4/pgAdmin4.py", line 87, in 
    exec(open(file_quote(setup_py), 'r').read())
  File "", line 449, in 
  File "", line 372, in setup_db
  
  [...]

  File "/home/mint/pgAdmin4/venv/lib/python3.8/site-packages/flask_sqlalchemy/__init__.py", line 575, in get_options
    self._sa.apply_driver_hacks(self._app, sa_url, options)
  File "/home/mint/pgAdmin4/venv/lib/python3.8/site-packages/flask_sqlalchemy/__init__.py", line 908, in apply_driver_hacks
    sa_url.database = os.path.join(app.root_path, sa_url.database)
AttributeError: can't set attribute

In the **second attempt** to execute pgAdmin4 the error shown is:

Traceback (most recent call last):
  File "/home/mint/pgAdmin4/venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 1705, in _execute_context
    self.dialect.do_execute(
  File "/home/mint/pgAdmin4/venv/lib/python3.8/site-packages/sqlalchemy/engine/default.py", line 681, in do_execute
    cursor.execute(statement, parameters)
sqlite3.OperationalError: table version already exists

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "venv/lib/python3.8/site-packages/pgadmin4/pgAdmin4.py", line 94, in 
    app = create_app()
  
  [...]

  File "/home/mint/pgAdmin4/venv/lib/python3.8/site-packages/sqlalchemy/engine/default.py", line 681, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) table version already exists
[SQL: 
CREATE TABLE version (
	name VARCHAR(32) NOT NULL, 
	value INTEGER NOT NULL, 
	PRIMARY KEY (name)
)

]
(Background on this error at: http://sqlalche.me/e/14/e3q8) 

This situation started to occur in March 2021 and as far as I know, it is identical on both Linux Mint 20 and Linux Mint 20.1. > Note: a more suitable location to put the virtualenv would have been /opt, but for multiple tests I opted for /home from a live USB with Linux Mint 20. Then apply the final changes to my Linux Mint 20.1