TST: Ignore floating point warning tests on MacOS

It is very much possible that this will also fail on other systems
and should rather only run, e.g. on newer glibc versions.

In principle, we could also split this into "no warnings given"
and "warning given".  MacOS seems very sloppy with floating point
warnings, but hopefully it at least does not give spurious ones.

Author: seberg

numpy/core/tests/test_umath.py

@@ -563,6 +563,9 @@ def test_float_remainder_roundoff(self):
                     else:
                         assert_(b > rem >= 0, msg)
 
+    @pytest.mark.xfail(sys.platform.startswith("darwin"),
+            reason="MacOS seems to not give the correct 'invalid' warning for "
+                   "`fmod`.  Hopefully, others always do.")
     @pytest.mark.parametrize('dtype', np.typecodes['Float'])
     def test_float_divmod_errors(self, dtype):
         # Check valid errors raised for divmod and remainder
@@ -586,6 +589,9 @@ def test_float_divmod_errors(self, dtype):
             # inf / 0 does not set any flags, only the modulo creates a NaN
             np.divmod(finf, fzero)
 
+    @pytest.mark.xfail(sys.platform.startswith("darwin"),
+           reason="MacOS seems to not give the correct 'invalid' warning for "
+                  "`fmod`.  Hopefully, others always do.")
     @pytest.mark.parametrize('dtype', np.typecodes['Float'])
     @pytest.mark.parametrize('fn', [np.fmod, np.remainder])
     def test_float_remainder_errors(self, dtype, fn):