Explicitly specify encoding.

The default encoding is utf-8, which is what we want, but it's confusing
not to specify it.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>

test/testfilemanip.py

@@ -132,7 +132,7 @@ class SHA256TransactionTest(unittest.TestCase):
         self.testcases = ["", "abc", "©", "\ufeff"]
 
     def generate_len_and_hash(self, func, data):
-        s = data.encode()
+        s = data.encode('utf-8')
         h = func()
         h.update(s)
         return "%s:%s" % (len(s), h.hexdigest())