Generalize database setup.

The new code does not depend on AssociationDBSqliteTask, except
through duck-typing, making it easier to add new DB implementations
in the future.

python/lsst/ap/pipe/ap_pipe.py

@@ -57,8 +57,7 @@
 from lsst.utils import getPackageDir
 from lsst.ip.diffim.getTemplate import GetCalexpAsTemplateTask
 from lsst.pipe.tasks.imageDifference import ImageDifferenceConfig, ImageDifferenceTask
-from lsst.ap.association import AssociationDBSqliteConfig, AssociationDBSqliteTask, \
-    AssociationConfig, AssociationTask
+from lsst.ap.association import AssociationDBSqliteTask, AssociationConfig, AssociationTask
 import lsst.daf.persistence as dafPersist
 
 # Names of directories containing data products in dataset_root
@@ -635,21 +634,19 @@ def doDiffIm(processed_repo, dataId, template, diffim_repo):
     return diffim_metadata
 
 
-def _makeAssociationDb(dbFile):
+def _setupDatabase(configurable):
     '''
-    Sets up an association database at the given location.
+    Sets up a database according to a configuration.
 
     Takes no action if the database already exists.
 
     Parameters
     ----------
-    dbFile: `str`
-        File on disk containing an sqlite3 database for storing and loading
-        DIASources and DIAObjects.
+    configurable: `lsst.pex.config.ConfigurableInstance`
+        A ConfigurableInstance with a database-managing class in its `target`
+        field. The `target`'s API must expose a `create_tables` method.
     '''
-    config = AssociationDBSqliteConfig()
-    config.db_name = dbFile
-    db = AssociationDBSqliteTask(config=config)
+    db = configurable.apply()
     try:
         db.create_tables()
     finally:
@@ -709,7 +706,7 @@ def doAssociation(diffim_repo, dataId, db_repo):
 
     butler = dafPersist.Butler(inputs=diffim_repo)
 
-    _makeAssociationDb(config.level1_db.db_name)
+    _setupDatabase(config.level1_db)
 
     associationTask = AssociationTask(config=config)
     try: