Revert "working on div's test_pipe_caller"

Revert "working on div's test_pipe_caller"

This reverts commit 8bf37997d31250126a664aeb3bd67ac0cd72a70c.

the build / install dependencies have not been properly documented,
making it impossible for anyone to install this at the moment.

that in turn makes it impossible for anyone to run:

* the div test_pipe_caller unit test
* the test_issuer.py test
* the test_core.py test
* the compunit test_div_compunit.py test

the modifications to caller.py whilst correct are reverted as a
side-effect due to violation of the development guidelines on
"single purpose commit"