In 3.0rc1, I get, for "make htmlhelp"

... contents copyright distutils/apiref Exception occurred:
  File
"/cygdrive/c/loewis/3k/python/Doc/tools/pygments/lexers/__init__.py", lin
e 83, in get_lexer_by_name
    raise ClassNotFound('no lexer for alias %r found' % _alias)
ClassNotFound: no lexer for alias 'python3' found

The full traceback is

Traceback (most recent call last):
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/__init__.py", line
128, in main
    app.build(all_files, filenames)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/application.py",
line 122, in build
    self.builder.build_update()
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/builder.py", line
242, in build_update
    'out of date' % len(to_build))
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/builder.py", line
282, in build
    self.write(docnames, updated_docnames, method)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/builder.py", line
319, in write
    self.write_doc(docname, doctree)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/builder.py", line
510, in write_doc
    self.docwriter.write(doctree, destination)
  File
"/cygdrive/c/loewis/3k/python/Doc/tools/docutils/writers/__init__.py",
line 78, in write
    self.translate()
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/htmlwriter.py",
line 32, in translate
    self.document.walkabout(visitor)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/docutils/nodes.py", line
159, in walkabout
    child.walkabout(visitor)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/docutils/nodes.py", line
159, in walkabout
    child.walkabout(visitor)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/docutils/nodes.py", line
159, in walkabout
    child.walkabout(visitor)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/docutils/nodes.py", line
159, in walkabout
    child.walkabout(visitor)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/docutils/nodes.py", line
159, in walkabout
    child.walkabout(visitor)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/docutils/nodes.py", line
151, in walkabout
    visitor.dispatch_visit(self)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/docutils/nodes.py", line
1502, in dispatch_visit
    return method(node)
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/htmlwriter.py",
line 191, in visit_literal_block
    lang, linenos))
  File "/cygdrive/c/loewis/3k/python/Doc/tools/sphinx/highlighting.py",
line 169, in highlight_block
    lexer = lexers[lang] = get_lexer_by_name(lang)
  File
"/cygdrive/c/loewis/3k/python/Doc/tools/pygments/lexers/__init__.py",
line 83, in get_lexer_by_name
    raise ClassNotFound('no lexer for alias %r found' % _alias)
ClassNotFound: no lexer for alias 'python3' found