Fix ctypes tests to avoid implicit bytes-unicode conversion
diff --git a/Lib/ctypes/test/test_python_api.py b/Lib/ctypes/test/test_python_api.py
index b74767a..1f4c603 100644
--- a/Lib/ctypes/test/test_python_api.py
+++ b/Lib/ctypes/test/test_python_api.py
@@ -72,10 +72,10 @@
         PyOS_snprintf.argtypes = POINTER(c_char), c_size_t, c_char_p
 
         buf = c_buffer(256)
-        PyOS_snprintf(buf, sizeof(buf), "Hello from %s", b"ctypes")
+        PyOS_snprintf(buf, sizeof(buf), b"Hello from %s", b"ctypes")
         self.assertEqual(buf.value, b"Hello from ctypes")
 
-        PyOS_snprintf(buf, sizeof(buf), "Hello from %s (%d, %d, %d)", b"ctypes", 1, 2, 3)
+        PyOS_snprintf(buf, sizeof(buf), b"Hello from %s (%d, %d, %d)", b"ctypes", 1, 2, 3)
         self.assertEqual(buf.value, b"Hello from ctypes (1, 2, 3)")
 
         # not enough arguments