fix qsscoring unit test

parasail produces slightly different alignments for one test case

modules/mol/alg/tests/test_qsscoring.py

 import unittest, os, sys
 import ost
-from ost import io, mol, settings
+from ost import io, mol, settings, seq
 # check if we can import: fails if numpy or scipy not available
 try:
   from ost.mol.alg.qsscoring import *
@@ -301,8 +301,18 @@ class TestQSscore(unittest.TestCase):
     ent_1 = _LoadFile('4dvh.1.pdb') # A2, symmetry: C2
     ent_2 = _LoadFile('4br6.1.pdb') # A4, symmetry: D2
     qs_scorer = QSscorer(ent_1, ent_2)
-    self.assertAlmostEqual(qs_scorer.global_score, 0.147, 2)
-    self.assertAlmostEqual(qs_scorer.best_score, 0.866, 2)
+
+    # The alignments from parasail slightly differ. The sequence identities
+    # are in the range 40% but slightly lower for parasail alignments.
+    # however, the parasail alignments appear less gappy and "nicer".
+    # They nevertheless lead to lower QS-score.
+    if seq.alg.ParasailAvailable():
+        self.assertAlmostEqual(qs_scorer.global_score, 0.14757304498883386, 2)
+        self.assertAlmostEqual(qs_scorer.best_score, 0.7878766697963304, 2)
+    else:
+        self.assertAlmostEqual(qs_scorer.global_score, 0.14797023263299844, 2)
+        self.assertAlmostEqual(qs_scorer.best_score, 0.8666616636985371, 2)
+
     self._CheckScorer(qs_scorer)
     # check properties
     self.assertFalse(qs_scorer.calpha_only)