db: remove redundant unique constraints from primary keys Primary keys are always unique, both in the SQL standard and in SQLite, MySQL and PostgreSQL. Setting unique=True cases SQLAlchemy to explicitly add additional, redundant UNIQUE indexes to the columns, which is at best needless metadata overhead, and at worst causes the database engine to waste time maintaining an extra index that serves no purpose.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
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