automation: delete code related to Python 2.7 support
The building of Inno and WiX installers took a python_version argument
that allowed us to specify "2" or "3" for the major Python version. Since
we no longer support Python 2, we can delete this argument and everything
feeding into it.
Differential Revision: https://phab.mercurial-scm.org/D12264
$ hg init
$ "$PYTHON" -c 'open("a", "wb").write(b"confuse str.splitlines\nembedded\rnewline\n")'
$ hg ci -Ama -d '1 0'
adding a
$ echo clean diff >> a
$ hg ci -mb -d '2 0'
$ hg diff -r0 -r1
diff -r 107ba6f817b5 -r 310ce7989cdc a
--- a/a Thu Jan 01 00:00:01 1970 +0000
+++ b/a Thu Jan 01 00:00:02 1970 +0000
@@ -1,2 +1,3 @@
confuse str.splitlines
embedded\r (no-eol) (esc)
newline
+clean diff