This is preferrable to writing in the current working directory because
it eliminates the risk to leak unwanted files, which can result in very
weird test failures.
Also this will help if we ever try to run these tests concurrently.
This commit touchs various parts of the code base and test framework. Any
found usage of opening a cursor for the sake of initializing a connection
has been replaced with 'ensure_connection()'.
Carl Meyer
Aymeric Augustin
Claude Paroz
Andrew Godwin
Michael Manfre