diff --git a/contrib/perf.py b/contrib/perf.py
--- a/contrib/perf.py
+++ b/contrib/perf.py
@@ -1058,7 +1058,7 @@
         elif isinstance(bundle, streamclone.streamcloneapplier):
             raise error.Abort(b'stream clone bundles not supported')
         else:
-            raise error.Abort(b'unhandled bundle type: %s' % type(bundle))
+            raise error.Abort(b'unhandled bundle type: %r' % type(bundle))
 
     for fn, title in benches:
         timer, fm = gettimer(ui, opts)
diff --git a/mercurial/bundlerepo.py b/mercurial/bundlerepo.py
--- a/mercurial/bundlerepo.py
+++ b/mercurial/bundlerepo.py
@@ -295,7 +295,7 @@
             self._cgunpacker = bundle
         else:
             raise error.Abort(
-                _(b'bundle type %s cannot be read') % type(bundle)
+                _(b'bundle type %r cannot be read') % type(bundle)
             )
 
         # dict with the mapping 'filename' -> position in the changegroup.
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -1567,7 +1567,7 @@
                 rev = self.changelog.rev(node)
             else:
                 raise error.ProgrammingError(
-                    b"unsupported changeid '%s' of type %s"
+                    b"unsupported changeid '%r' of type %r"
                     % (changeid, pycompat.sysstr(type(changeid)))
                 )
 
diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -597,7 +597,7 @@
     """
     if not isinstance(symbol, bytes):
         msg = (
-            b"symbol (%s of type %s) was not a string, did you mean "
+            b"symbol (%r of type %r) was not a string, did you mean "
             b"repo[symbol]?" % (symbol, type(symbol))
         )
         raise error.ProgrammingError(msg)
diff --git a/mercurial/utils/cborutil.py b/mercurial/utils/cborutil.py
--- a/mercurial/utils/cborutil.py
+++ b/mercurial/utils/cborutil.py
@@ -241,7 +241,7 @@
             break
 
     if not fn:
-        raise ValueError(b'do not know how to encode %s' % type(v))
+        raise ValueError(b'do not know how to encode %r' % type(v))
 
     return fn(v)