* Replace generic Exception with TemplateParserException.
* Add tests to cover many of the uncovered lines in
tools/lib/template_parser.py.
* Add an exclusion line to the naïve pattern for checking for missing
tuples in format strings, to keep the linter happy.
This starts to address 1533. I still think the </p> tags
should be on their own line lined up with the start tag,
so the linter won't let through the specific example
shown in the ticket.
Now, `tools/test-all` calls a new program called `tools/tests-tools`
that runs unit tests in `test_css_parser.py` and 'test_template_parser.py`.
This puts 100% line coverage on tools/lib/css_parser.py.
This puts about 50% line coverage on tools/lib/template_parser.py.