replace always by on_success in .gitlab-ci.yml and constrain center_date in...

replace always by on_success in .gitlab-ci.yml and constrain center_date in test to avoid edge effects

webgeodyn/tests/test_covobs_splines.py

@@ -25,7 +25,7 @@ class TestBuildingFromSplines(unittest.TestCase):
     def test_eval_derivate_spline(self):
         dt = 0.1
         t = np.arange(1980, 1990, dt)
-        center_date = np.random.choice(t)
+        center_date = np.random.choice(t[40:60]) #constraining center_date to narrower intervall to avoid edge effects.
         spl_order = 4
         knot_spacing = 1