This is in part so image_prep can run against an ancient CentOS 5 image
without any upfront help, and in part simply because it's very easy to
support.
This is needed to cope Ansible 2.3 doing weird stuff as usual. It serves
up __init__.py for ansible and ansible.module_utils as hard-coded
namespace packages, the real ansible/__init__.py on disk is not 2.4
compatible.
Making CallError inherit from object broke 'raise CallError()'.
Instead use pure-Python pickler on 2.4 (grmbl) and force it to emit
new-style-alike output for what is otherwise a classic class.
Remove needless complexity from _unpickle_call_error() that only worked
for new-style classes.
* origin/dmw:
issue #404: add to Changelog.
issue #251: readd to Changelog.
tests: add exact test for issue 251; closes#251.
issue #412: pad out debugging docs, add get_stack to changelog.
issue #412: force-verbose output for mitogen_get_stack.
issue #412: promote "mitogen_get_stack" to the main extension.
issue #412: add docstrings/boilerplate to transport_config.py.
issue #251, #412, #434: fix connection configuration brainwrong
issue #434: tests: set a default remote_user in ansible.cfg.
tests: CI should symlink all contents of ansible/hosts/
ansible: fix test failure during process exit.
tests: use assert_equal in more places.
tests: make assert_equal work on newer Ansibles.
tests: convert stack_construction.yml to assert_equal.
tests: make fork_histogram optional
tests: use assert_equal in delegate_to_template.yml.
tests: import assert_equal action.
tests: rename 'delegation/' to 'connection_delegation/'
core: replace ancient YOLO loop in fire().
tests: some more utility function tests + flake8.
tests: clean up / deduplicate Ansible inventory.
tests: add some more helper function tests.
David Wilson