tests/test-default-push.t

hghave: add "py3k" feature to check whether test runs with Python 3.x

This patch adds "py3k" feature to check whether test runs with Python
3.x.

This check is needed for portability of test code: for example, in the
default, modules are imported relatively first with python 2.x, but
imported absolutely with Python 3.x.

  $ hg init a

  $ echo a > a/a
  $ hg --cwd a ci -Ama
  adding a

  $ hg clone a c
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ echo b >> b/a
  $ hg --cwd b ci -mb

Push should push to 'default' when 'default-push' not set:

  $ hg --cwd b push
  pushing to $TESTTMP/a (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files

Push should push to 'default-push' when set:

  $ echo 'default-push = ../c' >> b/.hg/hgrc
  $ hg --cwd b push
  pushing to $TESTTMP/c (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files