diff -r 7ca8aa8840c0 -r 4e0a6d157910 mercurial/progress.py
--- a/mercurial/progress.py	Tue Dec 24 01:38:02 2019 -0500
+++ b/mercurial/progress.py	Thu Jan 02 17:27:37 2020 -0800
@@ -193,6 +193,7 @@
         if not self.printed or not self.lastprint or not shouldprint(self.ui):
             return
         self._writeerr(b'\r%s\r' % (b' ' * self.width()))
+        self._flusherr()
         if self.printed:
             # force immediate re-paint of progress bar
             self.lastprint = 0