fix: Allow non-ASCII values in all attributes

PR ietf-tools#1017 allowed Unicord characters everywhere.
This fixes a bug that xml2rfc was guarding against non-ASCII characters
in attribute values.
With `--warn-bare-unicode`, xml2rfc will warn if non-ASCII characters are
present in attribute values.

Fixes ietf-tools#1105

xml2rfc/writers/preptool.py

@@ -439,9 +439,9 @@ def check_attribute_values(self, e, p):
  if (c.tag, a) in latinscript_attributes:
  if not is_script(v, 'Latin'):
  self.err(c, 'Found non-Latin-script content in <%s> attribute value %s="%s"' % (c.tag, a, v))
- else:
+ if self.options.warn_bare_unicode:
  if not isascii(v):
- self.err(c, 'Found non-ASCII content in <%s> attribute value %s="%s"' % (c.tag, a, v))
+ self.warn(c, f'Found non-ASCII content in {c.tag} attribute value {a}="{v}" that should be inspected to ensure it is intentional.')
  if not (c.tag, a) in space_attributes:
  vv = v.strip()
  if vv != v: