diff -r fa30292b680b -r aa2e38147e8b mercurial/scmutil.py
--- a/mercurial/scmutil.py	Thu Feb 25 10:00:08 2021 -0500
+++ b/mercurial/scmutil.py	Thu Feb 25 10:08:33 2021 -0500
@@ -201,7 +201,9 @@
         msg = inst.args[1]
         if isinstance(msg, type(u'')):
             msg = pycompat.sysbytes(msg)
-        if not isinstance(msg, bytes):
+        if msg is None:
+            ui.error(b"\n")
+        elif not isinstance(msg, bytes):
             ui.error(b" %r\n" % (msg,))
         elif not msg:
             ui.error(_(b" empty string\n"))