--- a/mercurial/ui.py Thu Oct 12 19:20:04 2017 -0700
+++ b/mercurial/ui.py Thu Oct 12 23:30:46 2017 -0700
@@ -1041,7 +1041,7 @@
# gracefully and tell the user about their broken pager.
shell = any(c in command for c in "|&;<>()$`\\\"' \t\n*?[#~=%")
- if pycompat.osname == 'nt' and not shell:
+ if pycompat.iswindows and not shell:
# Window's built-in `more` cannot be invoked with shell=False, but
# its `more.com` can. Hide this implementation detail from the
# user so we can also get sane bad PAGER behavior. MSYS has