Resolve template path from package at configuration load time

[adiroiban]

We have the config.template as both a path or tuple(package_name, resource_name)

The loading is done here

towncrier/src/towncrier/_settings/load.py

Lines 187 to 203 in 68a7a3b

	# Process 'template'.
	markdown_file = Path(config.get("filename", "")).suffix == ".md"
	template = config.get("template", "towncrier:default")
	if re_resource_template.match(template):
	package, resource = template.split(":", 1)
	if not Path(resource).suffix:
	resource += ".md" if markdown_file else ".rst"
	if not _pkg_file_exists(package, resource):
	if _pkg_file_exists(package + ".templates", resource):
	package += ".templates"
	else:
	raise ConfigError(
	f"'{package}' does not have a template named '{resource}'.",
	failing_option="template",
	)
	template = (package, resource)

And then the actual path is resovled here

towncrier/src/towncrier/build.py

Lines 167 to 172 in 68a7a3b

	if isinstance(config.template, tuple):
	template = (
	resources.files(config.template[0])
	.joinpath(config.template[1])
	.read_text(encoding="utf-8")
	)

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I think that is best to resolve the full path when the configuration is loades so that config.template is always a text path.

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also see the converstation from #633 and see why the test pass when we don't add the special exception for a tuple.