This is a minor suggestion but might make it less confusing working with the library:

Spatial.importOSM() adds a layer when a file cannot be found. Since there are no stats shown in the output on number of nodes added etc, it appears as if the layer have been imported successfully when it hasn't.

neo4j@neo4j> CALL spatial.importOSM("london.osm");
Failed to invoke procedure spatial.importOSM: Caused by: java.io.FileNotFoundException: london.osm (No such file or directory)
neo4j@neo4j> CALL spatial.importOSM("london2.osm");
Failed to invoke procedure spatial.importOSM: Caused by: java.io.FileNotFoundException: london2.osm (No such file or directory)
neo4j@neo4j> CALL spatial.layers();
+-------------------------------------------------------------------------------------------+
| name | signature |
+-------------------------------------------------------------------------------------------+
| "london.osm" | "EditableLayer(name='london.osm', encoder=GeometryEncoder(bbox='bbox'))" |
| "london2.osm" | "EditableLayer(name='london2.osm', encoder=GeometryEncoder(bbox='bbox'))" |
+-------------------------------------------------------------------------------------------+

3 rows available after 3 ms, consumed after another 2 ms
neo4j@neo4j>