db: drop and re-create old schemas instead of Base.metadata.drop_all() Sadly, Base.metadata.drop_all() sometimes doesn't work because of foreign key constraints. We only know this is the case on PostgreSQL and MySQL - use workarounds for these.

# 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
.