Port practracker unit tests to python 3

scripts/maint/practracker/practracker_tests.py

@@ -4,7 +4,12 @@
 
 import unittest
 
-import StringIO
+try:
+    # python 2 names the module this way...
+    from StringIO import StringIO
+except ImportError:
+    # python 3 names the module this way.
+    from io import StringIO
 
 import metrics
 
@@ -38,7 +43,7 @@ fun,(
 
 class TestFunctionLength(unittest.TestCase):
     def test_function_length(self):
-        funcs = StringIO.StringIO(function_file)
+        funcs = StringIO(function_file)
         # All functions should have length 2
         for name, lines in metrics.get_function_lines(funcs):
             self.assertEqual(name, "fun")
@@ -50,7 +55,7 @@ class TestFunctionLength(unittest.TestCase):
 
 class TestIncludeCount(unittest.TestCase):
     def test_include_count(self):
-        f = StringIO.StringIO("""
+        f = StringIO("""
   #   include <abc.h>
   #   include "def.h"
 #include "ghi.h"