This is to workaround differences in minidom's pretty-printing that
occurred between Python 3.7 and 3.8.
* python/spot/jupyter.py (SVG): New class.
* python/spot/__init__.py: Use it.
* tests/python/_altscc.ipynb, tests/python/alternation.ipynb,
tests/python/automata.ipynb, tests/python/formulas.ipynb,
tests/python/gen.ipynb, tests/python/highlighting.ipynb,
tests/python/ltsmin-dve.ipynb, tests/python/ltsmin-pml.ipynb,
tests/python/product.ipynb, tests/python/randaut.ipynb,
tests/python/testingaut.ipynb, tests/python/twagraph-internals.ipynb,
tests/python/word.ipynb: Adjust.
e778965730