errorlib: wrap warnings to invenio.err
errorlib: wrap warnings to invenio.err

* Redirects captured warnings and corresponding
  tracebacks directly into invenio.err rather
  than polluting stderr and consequently apache.err.
  (closes #1616)

Signed-off-by: Samuele Kaplun <2e218f779e12714c314fad8ebf6b3041daa21337@cern.ch>
Tested-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio