absolute_import in datastore
update_library exception handling is in
no cross-table pk name clashes anymore
better setup of rethinkdb indexes
fixup! 6b4759c1fb37bb56bb0c53c39dac9a005c19c4a2
much improved get_missing_books; also allow filter by md5 hashes
pyflakes fix
fixup! f49bca766d60a49caa308143c515868fcf143330