"database is locked" eventually happens

[marado]

If I leave botany running for too long (possibly while other users run it, or also leave it running), eventually a "database is locked" error invades the screen.

Sorry that it wasn't possibly to copy paste the full trace well (the output mangled with botany's usual output), but that I captured provides the relevant parts:

self.run()
File "/usr/lib/python3.9/threading.py", line 892, in run
File "/    self._target(*self._args, **self._kwargs) _bootstrap_inner
File "/home/repos/botany/botany.py", line 434, in autosave
self.update_garden_db(this_plant)
File "/home/repos/botany/botany.py", line 517, in update_garden_db
self.init_database()
File "/home/repos/botany/botany.py", line 491, in init_database
c.execute(init_table_string)
sqlite3.OperationalError: database is locked

I could provide a patch to catch the error on init_database's execute, but before that it probably makes sense to decide what to do in these cases: while ignoring the failure is probably alright on autosave calls (the next autosave deals with it; we can also create a counter of consecutive fails to make sure it is only a sporadic concurrency issue), it probably is not in other calls. Also, it make sense investigating the root cause of the issue - who/what is locking the database for so long?

[epilys]

Some mitigations:

• set timeout before throwing the error: https://docs.python.org/3/library/sqlite3.html#sqlite3.connect
• check in_transaction() in python3 and busy wait until timeout
• using WAL as journal_mode: https://www.sqlite.org/wal.html