better platform test

Author: lkirk

python/tests/test_python_c.py

@@ -2053,7 +2053,7 @@ def norm_func(X, n, nA, nB):
         import platform
 
         # only run if we're not running on macos
-        if platform.mac_ver() != ("", ("", "", ""), ""):
+        if platform.system() not in {"Linux", "Windows"}:
             assert (ts_multi.get_num_sites(), ts_multi.get_num_sites()) == (56, 56)
             assert a.shape == (56, 56, 1)  # ts has 56 sites
         a = ts_multi.two_locus_count_stat(