test: make binary_sub python 2, 3 compatible

In order to access `stdin`, `stdout` as binary, you must use the
`buffer` member in Python 3.  The replacement of the binary data
requires that pattern and the replacement be byte objects.  Convert the
pattern and replacement to UTF-8 encoded bytes.

Author: compnerd

test/Serialization/Inputs/binary_sub.py

@@ -5,5 +5,9 @@
 (_, old, new) = sys.argv
 assert(len(old) == len(new))
 
-data = sys.stdin.read()
-sys.stdout.write(data.replace(old, new))
+if sys.version_info[0] < 3:
+    data = sys.stdin.read()
+    sys.stdout.write(data.replace(old, new))
+else:
+    data = sys.stdin.buffer.read()
+    sys.stdout.buffer.write(data.replace(old.encode('utf-8'), new.encode('utf-8')))