Disabling mouse-support from vim on Debian Stretch

For some insane reason, mouse support (via GPM) is enabled by default i vim on Debian Stretch (and maybe other, what do I know). Due to the equally insane practice of letting system defaults (from /usr/share/vim/vim80/defaults.vim) override site local configurations (from /etc/vim/vimrc), figuring out how to disable the madness was not trivial. Luckily though, the fix was simple enough once I figured it all out:

--- /etc/vim/vimrc-ORIG	2019-01-31 13:45:57.998082982 +0100
+++ /etc/vim/vimrc	2019-01-31 13:46:13.607915228 +0100
@@ -14,7 +14,9 @@
 " any settings in these files.
 " If you don't want that to happen, uncomment the below line to prevent
 " defaults.vim from being loaded.
-" let g:skip_defaults_vim = 1
+source $VIMRUNTIME/defaults.vim
+let g:skip_defaults_vim = 1
+set mouse =
 " Uncomment the next line to make Vim more Vi-compatible
 " NOTE: debian.vim sets 'nocompatible'.  Setting 'compatible' changes numerous