pycompat: remove large Python 2 block
We no longer support Python 2. So we can delete its compatibility
code and remove the conditional and dedent the Python 3 code.
In order to make the linter happy, we had to inline imports in the
stanza at the top of the file.
Differential Revision: https://phab.mercurial-scm.org/D12250
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..