lower precision of comparison for math tests a bit

CPython 3.7.3 wouldn't pass the current erfc test

Author: msimacek

graalpython/com.oracle.graal.python.test/src/tests/test_math.py

@@ -1332,7 +1332,7 @@ def executeFnTest(self, values, fn, fnName):
             else :
                 if result != expected:
                     if (sys.version_info.major >= 3 and sys.version_info.minor >= 5):
-                        self.assertTrue(math.isclose(result, expected, rel_tol=1e-14), "Test3 fail: {}({}) = {}, but was {}".format(fnName, value[0], expected, result))
+                        self.assertTrue(math.isclose(result, expected, rel_tol=1e-13), "Test3 fail: {}({}) = {}, but was {}".format(fnName, value[0], expected, result))
 
     def test_erf(self):
         erfValues = [(0.0,  0.0), (-0.0, -0.0), (INF,  1.0), (NINF,  -1.0), (NAN, NAN),