Fixed constant time compare tests so that they always use bytes as input.

Author: mark-adams

tests/test_compat.py

@@ -1,17 +1,24 @@
 from jwt.compat import constant_time_compare
 
 from .compat import unittest
+from .utils import ensure_bytes
 
 
 class TestCompat(unittest.TestCase):
     def setUp(self):  # noqa
         pass
 
     def test_constant_time_compare_returns_true_if_same(self):
-        self.assertTrue(constant_time_compare('abc', 'abc'))
+        self.assertTrue(constant_time_compare(
+            ensure_bytes('abc'), ensure_bytes('abc')
+        ))
 
     def test_constant_time_compare_returns_false_if_diff_lengths(self):
-        self.assertFalse(constant_time_compare('abc', 'abcd'))
+        self.assertFalse(constant_time_compare(
+            ensure_bytes('abc'), ensure_bytes('abcd')
+        ))
 
     def test_constant_time_compare_returns_false_if_totally_different(self):
-        self.assertFalse(constant_time_compare('abcd', 'efgh'))
+        self.assertFalse(constant_time_compare(
+            ensure_bytes('abcd'), ensure_bytes('efgh')
+        ))