See also <https://sqlite.org/c3ref/enable_shared_cache.html>. Apple basically disabled this function starting at macOS 10.7, that's why there's a warning.

It is possible to suppress the warning, but I don't think its worth the trouble.

BTW. The python documentation for this function claims this changes a thread-local setting, but the SQLite documentation says this is a process global setting in SQLite 3.5.0 and later (released in 2007).  It is possible to make behaviour match the python documentation by making _sqlite3.enable_shared_cache store a flag that's used in the call to sqlite3_open_v2. That would be a backward compatibility concern (there's bound to be users that rely on the current behavior), but would also avoid this warning.