story #7437: CSV import should raise a warning instead of an error

Change-Id: I9337c418ba39f8847649abb4ee75c3f4f06b1baf
Merge commit 'refs/changes/90/3090/1' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  story #7437: CSV import should raise a warning instead of an error
This is Tuleap 7.5.99.35

Change-Id: I40c706092ea2f1f04a5d5b1c315c3a59264623f2