Cinemasci: Using cinema view doesn't work, uncaught syntax error parsing json

@dhr @utkarsh.ayachit

I am testing on macos with a build from source of the release branch, enabling python

I am trying to look at this cdb test_cdb_static_camera.cdb.tar.gz with:

~/projects/paraview/release-build/bin/pvpython -m paraview.tpl.cinemasci.server --viewer view --data test_cdb_static_camera.cdb --port 8001

The page loads, but without images. Looking in the console, I am getting this error:

Uncaught SyntaxError: JSON.parse: unexpected end of data at line 1 column 1 of the JSON data
    <anonymous> http://127.0.0.1:8001/:70
    onreadystatechange http://127.0.0.1:8001/:108
127.0.0.1:8001:70:33
    <anonymous> http://127.0.0.1:8001/:70
    onreadystatechange http://127.0.0.1:8001/:108

The same database works with cinema explorer:

~/projects/paraview/release-build/bin/pvpython -m paraview.tpl.cinemasci.server --viewer explorer --data test_cdb_static_camera.cdb --port 8002