diff --git a/contrib/python3-whitelist b/contrib/python3-whitelist
--- a/contrib/python3-whitelist
+++ b/contrib/python3-whitelist
@@ -51,6 +51,7 @@ test-cat.t
 test-cbor.py
 test-censor.t
 test-changelog-exec.t
+test-check-code.t
 test-check-commit.t
 test-check-execute.t
 test-check-interfaces.py
diff --git a/tests/test-check-code.t b/tests/test-check-code.t
--- a/tests/test-check-code.t
+++ b/tests/test-check-code.t
@@ -22,7 +22,7 @@ New errors are not allowed. Warnings are
   >>> commands = []
   >>> with open('mercurial/debugcommands.py', 'rb') as fh:
   ...     for line in fh:
-  ...         m = re.match("^@command\('([a-z]+)", line)
+  ...         m = re.match(b"^@command\('([a-z]+)", line)
   ...         if m:
   ...             commands.append(m.group(1))
   >>> scommands = list(sorted(commands))