Issues with type hints for `urllib.parse.urldefrag`

[mr-c]

• PY3: reveal_type(urldefrag(...)[1]) should retain the type of the input instead of Any
• PY2: reveal_type(urldefrag(...)[1]) should not be fixed as str; should be unicode when a unicode input is provided
• PY2: type for urldefrag should be updated to allow unicode input

from six.moves import urllib
from typing_extensions import TYPE_CHECKING

if not TYPE_CHECKING:
    def reveal_type(ignored):
        pass

_, frg = urllib.parse.urldefrag("https://github.com/python/typeshed/#typeshed")
print(type(frg))
reveal_type(frg)

_, frg2 = urllib.parse.urldefrag(u"https://github.com/python/typeshed/#typeshed")
print(type(frg2))
reveal_type(frg2)

_, frg3 = urllib.parse.urldefrag(b"https://github.com/python/typeshed/#typeshed")
print(type(frg3))
reveal_type(frg3)

$ mypy  typing-defrag-test.py                                                                                          
typing-defrag-test.py:11: error: Revealed type is 'Any'
typing-defrag-test.py:15: error: Revealed type is 'Any'
typing-defrag-test.py:19: error: Revealed type is 'Any'

$ mypy --py2  typing-defrag-test.py                                                                                    
typing-defrag-test.py:11: error: Revealed type is 'builtins.str'
typing-defrag-test.py:13: error: Argument 1 to "urldefrag" has incompatible type "unicode"; expected "str"
typing-defrag-test.py:15: error: Revealed type is 'builtins.str'
typing-defrag-test.py:19: error: Revealed type is 'builtins.str'

$ python3 typing-defrag-test.py                                                                                         
<class 'str'>
<class 'str'>
<class 'bytes'>

$ python2 typing-defrag-test.py                                                                                        
<type 'str'>
<type 'unicode'>
<type 'str'>

$ mypy --version
mypy 0.630
$ python -V
Python 2.7.15+
$ python3 -V
Python 3.6.6+

[mr-c]

This is still occurring :-P

[AlexWaygood]

I've ticked off the Python-2-specific items, since we'll soon be dropping support for Python 2 entirely ( #7367). The Python-3 issue still reproduces, though.