Fix libc++ pretty printer test for Python 3 after D67238

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@373452 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/pretty_printers/gdb_pretty_printer_test.py b/test/pretty_printers/gdb_pretty_printer_test.py
index 5e42568..b738c72 100644
--- a/test/pretty_printers/gdb_pretty_printer_test.py
+++ b/test/pretty_printers/gdb_pretty_printer_test.py
@@ -51,7 +51,7 @@
                 test_fails = not re.match(check_literal, value)
             else:
                 check_literal_string = expectation_val.string(encoding="utf-8")
-                check_literal = check_literal_string.encode("utf-8")
+                check_literal = str(check_literal_string.encode("utf-8"))
                 test_fails = value != check_literal
 
             if test_fails: