Label has disallowed hyphens

[quantenschaum]

Consider the following

Python 2.7.12 (default, Jul  1 2016, 15:12:24) 
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import idna
>>> idna.encode('r6---sn-i5onxoxu-cxgl.c.doc-0-0-sj.sj.googleusercontent.com')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/idna/core.py", line 355, in encode
    result.append(alabel(label))
  File "/usr/local/lib/python2.7/dist-packages/idna/core.py", line 276, in alabel
    check_label(label)
  File "/usr/local/lib/python2.7/dist-packages/idna/core.py", line 239, in check_label
    check_hyphen_ok(label)
  File "/usr/local/lib/python2.7/dist-packages/idna/core.py", line 134, in check_hyphen_ok
    raise IDNAError('Label has disallowed hyphens in 3rd and 4th position')
idna.core.IDNAError: Label has disallowed hyphens in 3rd and 4th position

Same issue for decoding. The hostname is valid, so it should just pass without error.

I came here because requests unconditionally does idna encoding of the hostname.

[kjd]

On first glance, this looks like it is the same issue as #27 which is not a bug in the library but an illegal hostname. Will investigate further.