Bump graphviz from 0.17 to 0.18.1

[dependabot]

Bumps graphviz from 0.17 to 0.18.1.

Changelog

Sourced from graphviz's changelog.

Version 0.18.1

Fix TypeError: argument of type 'WindowsPath' is not iterable on Windows platform under Python 3.6 and 3.7 (work around https://bugs.python.org/issue41649).

Update outdated examples source links.

Improve mode structure and separation of concerns.

Improve test structure and coverage.

Improve output of try-examples.py. Add exit status for CI. Disable view().

Add build-docs.py script for development.

Add update-help.py script for development.

Version 0.18

Change of beaviour: File endings are now normalized so that all DOT source outputs end with a final newline (Unix convention, simplifies concatenation). This includes DOT source files written by .render(), .view(), or .save() as well was .source generated or loaded from Source (or Source.from_file()).

Change of behaviour: Source instances created by Source.from_file() no nonger write the content read into .source back into the file. Use .save(skip_existing=False) before calling .render() or .view() if you want to overwrite the file to produce the previous (less safe) behaviour.

Change of undocumented behaviour: When iterating over a Graph, Digraph, or Source instance, the yielded lines now include a final newline ('\n'). This mimics iteration over file object lines in text mode.

When passing invalid parameters such as unknown engine, format, etc., .render() now raises early before writing the file. Call .save() explicitly to produce the previous (less safe) behaiour.

Add optional keyword-only encoding argument to pipe(). Returns the decoded stdout from the rendering process (e.g. format='svg'). Delegates encoding/decoding to subprocess in the common case

... (truncated)

Commits

• 8fc35da release 0.18.1
• ef4b99f document remaining changes since 0.18
• 2a72fb8 replace Path instances with their str() in execution: Windows, Python before 3.8
• 2923487 add docstring
• 967f7e7 skip viewing and add try-example.py exit status
• 2cfc6ae add filename to colors.py and structs.py examples
• ce12846 reduce line searching
• 40f4545 save a pair of lines
• 5a72e75 save a line
• d4897ea use utf-8 in doctests (second service)
• Additional commits viewable in compare view

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[dependabot]

Superseded by #37.