check-py3-compat: drop support for Python 2 We no longer support Python 2 so we can drop support for linting code for Python 2 support. This gets rid of the check for `from __future__`, enabling us to delete those imports. Differential Revision: https://phab.mercurial-scm.org/D12251

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