Three dots (...) in relative import not accepted

[JukkaL]

If you have ... in a relative import, the parser crashes:

from ... import a

Here's the stack trace:

Traceback (most recent call last):
  File "scripts/mypy", line 169, in <module>
    main()
  File "scripts/mypy", line 34, in main
    type_check_only(path, module, bin_dir, options)
  File "scripts/mypy", line 78, in type_check_only
    python_path=options.python_path)
  File "/home/jukka/project/mypy/mypy/build.py", line 164, in build
    result = manager.process(UnprocessedFile(info, program_text))
  File "/home/jukka/project/mypy/mypy/build.py", line 342, in process
    next.process()
  File "/home/jukka/project/mypy/mypy/build.py", line 660, in process
    tree = self.parse(self.program_text, self.path)
  File "/home/jukka/project/mypy/mypy/build.py", line 739, in parse
    custom_typing_module=self.manager.custom_typing_module)
  File "/home/jukka/project/mypy/mypy/parse.py", line 80, in parse
    tree = parser.parse(s)
  File "/home/jukka/project/mypy/mypy/parse.py", line 117, in parse
    file = self.parse_file()
  File "/home/jukka/project/mypy/mypy/parse.py", line 125, in parse_file
    defs = self.parse_defs()
  File "/home/jukka/project/mypy/mypy/parse.py", line 248, in parse_defs
    defn, is_simple = self.parse_statement()
  File "/home/jukka/project/mypy/mypy/parse.py", line 668, in parse_statement
    stmt = self.parse_import_from()
  File "/home/jukka/project/mypy/mypy/parse.py", line 176, in parse_import_from
    name = self.parse_qualified_name()
  File "/home/jukka/project/mypy/mypy/parse.py", line 234, in parse_qualified_name
    tok = self.expect_type(Name)
  File "/home/jukka/project/mypy/mypy/parse.py", line 1529, in expect_type
    self.parse_error()
  File "/home/jukka/project/mypy/mypy/parse.py", line 1547, in parse_error
    self.parse_error_at(self.current())
  File "/home/jukka/project/mypy/mypy/parse.py", line 1558, in parse_error_at
    msg = 'Parse error before {}'.format(token_repr(tok))
  File "/home/jukka/project/mypy/mypy/parse.py", line 1672, in token_repr
    raise ValueError('Unknown token {}'.format(repr(tok)))
ValueError: Unknown token EllipsisToken( ...)