The attached file demonstrates two bugs regarding the task juggler
exporter. I load the ox-taskjuggler file and export with the key
sequence C-c C-e J j

1. SCHEDULED date is not exported as a start attribute.
2. The BLOCKER attribute requires a space between two dependency
tasks. For example, Task 3 in the attached file depends on Task 1 and
Task 2. Setting :BLOCKER:  aa,bb has no impact on the generated
file. The attribute is ignored. If I set :BLOCKER:  aa, bb (note the
space between aa and bb), the produced file declares the dependency.