Fixed skip condition in ticker test

Author: niederha

tests/test_Ticker.py

@@ -5,12 +5,15 @@
 
 from roboticstoolbox.tools.Ticker import Ticker
 import unittest
+import platform
 
 
 class TestTicker(unittest.TestCase):
 
     def test_ticker(self):
-        self.skipTest('Not working on windows or mac')
+
+        if platform.system() in ['Windows', 'Darwin']:
+            self.skipTest('Not working on windows or mac')
 
         t = Ticker(0.1)