[core][workflow] add unit test with some larch and pymca process meld.

xftf fails because chi is not setted by exafs. Could it be computed from outside ?
4 jobs for unit_test_pymca_larch in 5 minutes and 47 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #45493
test:python3.5-stretch-pyqt5_larch

00:03:43

passed #45492
test:python3.5-stretch-pyqt5_pymca

00:05:33

passed #45494
test:python3.5-stretch-pyqt5_pymca_larch

00:05:46

passed #45495
test:test-xas-tutorials_pymca

00:04:23