Fix in test_dch.py failing test_selected_idx_and_scores due to sign flip(s) in PCA

With version changes of the of sklearn the PCA output can have sign
flips of the principal components. Now we only compare the absolute
value to make the test invariant to such sign changes.

Author: ceriottm

tests/test_dch.py

@@ -30,7 +30,8 @@ def test_selected_idx_and_scores(self):
         selector.fit(self.T, self.y)
         self.assertTrue(np.allclose(selector.selected_idx_, self.idx))
 
-        feature_residuals = selector.score_feature_matrix(self.T)
+        # takes abs to avoid numerical noise changing the sign of PCA projections
+        feature_residuals = np.abs(selector.score_feature_matrix(self.T))
         val = np.max(
             np.abs(
                 (self.feature_residuals_100 - feature_residuals[100])