/etc/mercurial/hgrc.d/qct.rc is in qct 1.7-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 | #
# if you remove the qct package without purging it, this conffile
# will be kept and mercurial will try to load the (removed) qct extension
# so it will emit a warning
#
# Two fix are possible in this case:
# 1: purging the qct package (with "apt-get remove --purge qct" for example)
# 2: commenting the line requesting the extension below
[extensions]
hgext.qct =
|