Make FTMstore cross-compatible with SQLAlchemy 1.4 and 2+

[catileptic]

• run the SQLAlchemy tests with a Postgres connection
• use the future=True flag in the create_engine method in order to use the SQLA 2+ API in SQLA 1.4 (as per the docs)

Without passing the future=True flag in the create_engine method, the following exception occurs when running the tests with SQLAlchemy 1.4:

[...]
            with self.store.engine.connect() as conn:
                conn.execute(stmt)
>               conn.commit()
E               AttributeError: 'Connection' object has no attribute 'commit'

ftmstore/dataset.py:77: AttributeError
[...]
RemovedIn20Warning: Deprecated API features detected! These feature(s) are not compatible with SQLAlchemy 2.0. To prevent incompatible upgrades prior to updating applications, ensure requirements files are pinned to "sqlalchemy<2.0". Set environment variable SQLALCHEMY_WARN_20=1 to show all deprecation warnings.  Set environment variable SQLALCHEMY_SILENCE_UBER_WARNING=1 to silence this message. (Background on SQLAlchemy 2.0 at: https://sqlalche.me/e/b8d9)
    conn.execute(stmt)

[tillprochaska]

requirements.txt still requires 2.0.x. That seems unintended?

[catileptic]

requirements.txt isn't used then running pip install. It's usually used for local dev or when a Docker image specifically runs pip install -r requirements.txt for a repo. In my view, it's fine is the version of SQLAlchemy stays pinned in requirements.txt, especially if it's pinned to v2, since that's ultimately what we want all these libs to use.

LE: setup.py in our case is what is used when running pip install (or when building a lib and uploading it to PyPI).

[tillprochaska]

Ah, sorry, I checked setup.py but that doesn’t specify any dependencies at all and I had assumed it would fall back to requirements.txt in that case of something like that. But I just tried this out in a fresh venv…

pip3 install git+https://github.com/alephdata/followthemoney-store.git@chore/sqla-1.4-2-compatibility
python3 -c "python3 -c "import sqlalchemy; print(sqlalchemy.__version__)"

… and it turns out that SQLAlchemy isn’t installed at all in this case and would need to be installed manually. I’m fine with this PR then, but maybe we should consider specifying dependencies in setup.py (either in this PR or in a separate PR)?