[repository] drop remanescence of old multi-sources code
we don't use anymore this inputmap/varmap thing.
3.23 (UNRELEASED)
=================
Backwards-incompatible changes
------------------------------
* Generative tests *à la logilab-common* are not supported anymore in
`CubicWebTC`. It is advised to use the subtests_ API (available on
`CubicWebTC` either from the standard library as of Python 3.4 or through
unittest2 package otherwise).
.. _subtests: https://docs.python.org/3/library/unittest.html#distinguishing-test-iterations-using-subtests