--- a/mercurial/scmutil.py	Tue Nov 19 23:19:57 2019 +0900
+++ b/mercurial/scmutil.py	Wed Dec 18 20:17:21 2019 +0100
@@ -262,7 +262,7 @@
             if isinstance(reason, pycompat.unicode):
                 # SSLError of Python 2.7.9 contains a unicode
                 reason = encoding.unitolocal(reason)
-            ui.error(_(b"abort: error: %s\n") % reason)
+            ui.error(_(b"abort: error: %s\n") % stringutil.forcebytestr(reason))
         elif (
             util.safehasattr(inst, b"args")
             and inst.args