https://bz.mercurial-scm.org/show_bug.cgi?id=6913

--- mercurial-6.8.1/tests/testlib/wait-on-file.orig
+++ mercurial-6.8.1/tests/testlib/wait-on-file
@@ -29,7 +29,7 @@
     touch "$create"
     create=""
 fi
-while [ "$timer" -gt 0 ] && !([ -e "$wait_on" ] || [ -L "$wait_on" ]) ; do
+while [ "$timer" -gt 0 ] && ! ([ -e "$wait_on" ] || [ -L "$wait_on" ]) ; do
     timer=$(( $timer - 1))
     sleep 0.02
 done