tests/testlib/common.sh

py2: drop some more from __future__ statements

These are no longer needed after dropping support for Python 2.

Differential Revision: https://phab.mercurial-scm.org/D12258

mkcommit() {
   name="$1"
   shift
   echo "$name" > "$name"
   hg add "$name"
   hg ci -m "$name" "$@"
}