Need an error if you use postgis input without having it installed

[mapnik@…]

When using Mapnik and the PostGIS input driver, if you don't have the postgis driver installed mapnik simply assumes no data exists for the layer and continues on, when instead it should throw an error of some kind.

Steps to reproduce:

• Build Mapnik without the PostGIS driver
• Ask it to render a map that uses a PostGIS source

Expected behaviour:

• Mapnik errors, telling you that the driver doesn't exist.

Actual behaviour:

• Mapnik assumes the layer is blank, and renders an entirely blank map.

[dave]

This has been fixed as far as I can tell. If I remove the shape plugin, or try load a PostGIS datasource (I haven't built the PostGIS input plugin), I get an error:

Traceback (most recent call last):

File "displacement.py", line 64, in <module>

road_layer.datasource = Shapefile(file='../data/test/displacement')

File "/usr/lib/python2.5/site-packages/mapnik/init.py", line 72, in Shapefile

return CreateDatasource?(keywords)

UserWarning?: Could not create datasource. No plugin found for type 'shape'

---

Traceback (most recent call last):

File "displacement.py", line 68, in <module>

table='bmpolygon_joined_current')

File "/usr/lib/python2.5/site-packages/mapnik/init.py", line 76, in PostGIS

return CreateDatasource?(keywords)

UserWarning?: Could not create datasource. No plugin found for type 'postgis'

[dave]

Duplicate ticket #21