diff --git a/contrib/python3-whitelist b/contrib/python3-whitelist
--- a/contrib/python3-whitelist
+++ b/contrib/python3-whitelist
@@ -392,6 +392,7 @@ test-obsolete-distributed.t
 test-obsolete-divergent.t
 test-obsolete-tag-cache.t
 test-obsolete.t
+test-pager-legacy.t
 test-pager.t
 test-parents.t
 test-parseindex2.py
diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -1076,7 +1076,8 @@ class ui(object):
             if name not in encoding.environ:
                 pagerenv[name] = value
 
-        self.debug('starting pager for command %r\n' % command)
+        self.debug('starting pager for command %s\n' %
+                   stringutil.pprint(command))
         self.flush()
 
         wasformatted = self.formatted()