rasterstorer: WCSTImport error No JSON object could be decoded

[howff]

When I try to import a raster file with rasterstorer I get this error:

[2017-12-01 11:49:00,378: INFO/PoolWorker-1] rasterstorer.import[88c7af16-51b9-4805-97b7-e1f6c64ccd60]: [Raster_InsertCoverage] Executing WCSTImport request to:http://rasdaman:8080/rasdaman/ows/wcs/ with param: bnBwZG5iZGF5c2RyLjE3MzE5MTMxMjU0LnRpZg==
[2017-12-01 11:49:00,386: INFO/PoolWorker-1] rasterstorer.import[88c7af16-51b9-4805-97b7-e1f6c64ccd60]: [Raster_Import]Resource 6b3758ef-4a81-4b63-ad4c-ed6badc77d5a could not be imported. Exception message: No JSON object could be decoded

My config is
ckanext.publicamundi.rasterstorer.url = http://rasdaman:8080/rasdaman/ows
ckanext.publicamundi.rasterstorer.wcst_base_url = http://rasdaman:8080/rasdaman/ows
ckanext.publicamundi.rasterstorer.wcst_import_url = http://rasdaman:8080/rasdaman/ows/wcs
and those URLs seem to be correct.