---------------------------
Backwards incompatible improvements to :func:`~humanfriendly.testing.run_cli()`.
I just wasted quite a bit of time debugging a Python 3.6 incompatibility in
deb-pkg-tools (see build 251688788_) which was obscured by my naive
implementation of the ``run_cli()`` function. This change is backwards
incompatible because ``run_cli()`` now intercepts all exceptions whereas
previously it would only intercept ``SystemExit``.
.. _Release 4.0: https://github.com/xolox/python-humanfriendly/compare/3.8...4.0
.. _251688788: https://travis-ci.org/xolox/python-deb-pkg-tools/builds/251688788