fix test suite (pytest changes in ExceptionInfo class)
diff --git a/tests/test_eigen.py b/tests/test_eigen.py
index 45f64ca..55d9351 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen.py
@@ -679,10 +679,10 @@
     # These should still fail (incompatible dimensions):
     with pytest.raises(TypeError) as excinfo:
         m.iss1105_row(np.ones((7, 1)))
-    assert "incompatible function arguments" in str(excinfo)
+    assert "incompatible function arguments" in str(excinfo.value)
     with pytest.raises(TypeError) as excinfo:
         m.iss1105_col(np.ones((1, 7)))
-    assert "incompatible function arguments" in str(excinfo)
+    assert "incompatible function arguments" in str(excinfo.value)
 
 
 def test_custom_operator_new():