TST: Check pytables<3.5.1 when skipping

3.5.1 was made available on conda, causing
'xfail_non_writeable' tests to fail.

Author: gfyoung

pandas/tests/io/test_pytables.py

@@ -38,7 +38,8 @@
 # remove when gh-24839 is fixed; this affects numpy 1.16
 # and pytables 3.4.4
 xfail_non_writeable = pytest.mark.xfail(
-    LooseVersion(np.__version__) >= LooseVersion('1.16'),
+    LooseVersion(np.__version__) >= LooseVersion('1.16') and
+    LooseVersion(tables.__version__) < LooseVersion('3.5.1'),
     reason=('gh-25511, gh-24839. pytables needs a '
             'release beyong 3.4.4 to support numpy 1.16x'))