I am using Alembic for migrations implementation in a Flask project. There is a alembic.ini file where the database configs must be specified:
Flask
alembic.ini
I've solved the problem by setting sqlalchemy.url in env.py as @dirn suggested.
sqlalchemy.url
env.py
config.set_main_option('sqlalchemy.url', ) did the trick, where can be loaded from environment or config file.
config.set_main_option('sqlalchemy.url', )