Skip numpy inline test rather than discarding it if numpy is not installed.

Cython/Build/Tests/TestInline.py

-import os, tempfile
+import os
+import tempfile
+import unittest
 from Cython.Shadow import inline
 from Cython.Build.Inline import safe_type
 from Cython.TestUtils import CythonTest
@@ -86,8 +88,7 @@ class TestInline(CythonTest):
             2.5
         )
 
-    if has_numpy:
-
+    @unittest.skipIf(not has_numpy, "NumPy is not available")
     def test_numpy(self):
         import numpy
         a = numpy.ndarray((10, 20))