Add develover sql switch

If you want to play with the current state of sql, you need
a switch to turn it on. So here is the super secret
developer switch.

So you want to know where it is?

Here it is:

Create a file mediagoblin/db/sql_switch.py and put one line
in it: "use_sql = True" (or False to disable again). Right,
that's it. If you want to delete it, remember to delete the
*.pyc too.

Be careful not to "git add" it by accident!

mediagoblin/db/open.py

@@ -14,5 +14,14 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from mediagoblin.db.mongo.open import \
-    setup_connection_and_db_from_config, check_db_migrations_current
+try:
+    from mediagoblin.db.sql_switch import use_sql
+except ImportError:
+    use_sql = False
+
+if use_sql:
+    from mediagoblin.db.sql.open import \
+        setup_connection_and_db_from_config, check_db_migrations_current
+else:
+    from mediagoblin.db.mongo.open import \
+        setup_connection_and_db_from_config, check_db_migrations_current

mediagoblin/db/util.py

@@ -14,5 +14,12 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from mediagoblin.db.mongo.util import (ObjectId, InvalidId,
-    DESCENDING)
+try:
+    from mediagoblin.db.sql_switch import use_sql
+except ImportError:
+    use_sql = False
+
+if use_sql:
+    from mediagoblin.db.sql.fake import ObjectId, InvalidId, DESCENDING
+else:
+    from mediagoblin.db.mongo.util import ObjectId, InvalidId, DESCENDING