cleanup sqlitedb temporary db file after tests

[minrk]

Avoids

...
[Application] Table _ exists and doesn't match db format, trying __1
[Application] keys mismatch

messages in the test suite, which could happen if the test suite was run in relatively quick succession across db-format changes.

[fperez]

Wouldn't it be better for that file to be created with tempfile instead of having a fixed 'tasks.db' name? That way, a stray /tmp/tasks.db file can't cause problems. A scenario where that could occur: user 1 runs the suite before this cleanup fix or with a crash that for some reason prevents cleanup, then user 2 on the same machine can't run the tests anymore because he can't create/write to /tmp/tasks.db. Making that filename with the tempfile machinery will prevent this, it can be simply a module-level global created in setup() and deleted in teardown() just like now, but with a random name made by tempfile.

[minrk]

Sensible, I'll write that up now.

[fperez]

Awesome, thx. I'll review and merge quickly.

[minrk]

setup() now creates full temp file.

[fperez]

Perfect, thanks! Merging now.