Fix test checkpoint reporter close file before repoening

wrappers/python/tests/TestCheckpointReporter.py

+import os
 import unittest
 import tempfile
 import numpy as np
@@ -18,7 +19,7 @@ class TestCheckpointReporter(unittest.TestCase):
         self.simulation.context.setPositions(pdb.positions)
 
     def test_1(self):
-        file = tempfile.NamedTemporaryFile()
+        file = tempfile.NamedTemporaryFile(delete=False)
         self.simulation.reporters.append(app.CheckpointReporter(file, 1))
         self.simulation.step(1)
 
@@ -27,9 +28,10 @@ class TestCheckpointReporter(unittest.TestCase):
         # now set the positions into junk...
         self.simulation.context.setPositions(np.random.random(positions.shape))
         # then reload the right positions from the checkpoint
+        file.close()
         with open(file.name, 'rb') as f:
             self.simulation.context.loadCheckpoint(f.read())
-        file.close()
+        os.unlink(file.name)
 
         newPositions = self.simulation.context.getState(getPositions=True).getPositions(asNumpy=True)._value
         np.testing.assert_array_equal(positions, newPositions)