diff -r c5548b0b6847 -r ef43765c921d mercurial/utils/procutil.py
--- a/mercurial/utils/procutil.py	Thu Nov 14 13:38:17 2019 -0500
+++ b/mercurial/utils/procutil.py	Thu Nov 14 14:03:02 2019 -0800
@@ -289,7 +289,7 @@
         elif (
             not pycompat.iswindows
             and os.path.basename(
-                pycompat.fsencode(getattr(mainmod, '__file__', b''))
+                pycompat.fsencode(getattr(mainmod, '__file__', ''))
             )
             == b'hg'
         ):