Idle postgres connection interferes with some automated testing frameworks

[artemp]

Using django testing framework, some unit tests were written that generate a basic default map which draws from postgis.

The db connection stays open (due to connection pooling?). While this is good behavior in production, the testing framework creates a test db, runs tests then destroys the test db as the final step. Because mapnik still has an idle postgres connection, the test script throws an exception:

psycopg2.OperationalError: database "test_simple1" is being accessed by other users
DETAIL: There are 1 other session(s) using the database.

It would be nice to have a way to control this connection behavior via the mapnik API.

[artemp]

[springmeyer] see #433 where I experimenting with the connection being closed when the datasource object is deleted rather than when mapnik exits (and releases the Connection Manager). I think the latter behavior is likely ideal, but perhaps we could add keyword arg to the postgis layer to control this....

[artemp]

[springmeyer] Keyword arg added to patch at #433 which maintains current behavior but allows the desired control.

When you set:

persist_connection = false

in the params of one of the postgres layers loaded via xml, then call

del map

and the connection should be closed.

[artemp]

[perrygeo] Setting persist_connection to false appears to work - regardless of using "del map" or not.

[artemp]

[springmeyer] great, applied in r1337