Logging for debug output
------------------------

Matplotlib has in the past (sporadically) used an internal
verbose-output reporter.  This version converts those calls to using the
standard python `logging` library.

Support for the old ``rcParams`` ``verbose.level`` and ``verbose.fileo`` is
dropped.

The command-line options ``--verbose-helpful`` and ``--verbose-debug`` are
still accepted, but deprecated.  They are now equivalent to setting
``logging.INFO`` and ``logging.DEBUG``.

The logger's root name is ``matplotlib`` and can be accessed from programs
as::

  import logging
  mlog = logging.getLogger('matplotlib')

Instructions for basic usage are in :ref:`troubleshooting-faq` and for
developers in :ref:`contributing`.

.. _logging: https://docs.python.org/3/library/logging.html