Graphviz

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Add ``format`` argument to ``Graph/Digraph.render()``. This follows stand-alone
``render()`` function and mirrors the ``Graph/Digraph.pipe()`` method (usually,
``format`` is set on the instance).

Add ``renderer`` and ``formatter`` arguments to ``Graph/Digraph.render()`` and
``pipe()`` methods, as well as stand-alone ``render()`` and ``pipe()`` functions.

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Use ``sys.stderr`` to write stderr output from rendering process to stderr
(instead of file descriptor inheritance). Ensures stderr is passed in special
environments such as IDLE.

Suppress rendering process ``stdout`` in ``render()``.

Make ``quiet=True`` also suppress ``stderr`` on success of ``render()`` and
``pipe()`` (exit-status ``0``).

Include ``stderr`` from rendering process in ``CalledProcessError`` exception.

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Tag Python 3.7 support (work around subprocess ``close_fds`` issue on Windows).

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Fix compatibility with ``python -OO``.

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Add ``nohtml()`` to support labels of the form ``'<...>'`` (disabling their default
treatment as HTML strings).

Make default ``'utf-8'`` ``encoding`` more visible.

Set ``encoding = locale.getpreferredencoding()`` when ``encoding`` argument/property is
set to ``None`` explicitly (follow stdlib ``io.open()`` behaviour).

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Add ``Source.from_file()``-classmethod (simpler in-line SVG display of ready-made
.gv files within Jupyter).

Drop Python 3.3 support.