Fix/change deprecated function calls

[MSeifert04]

This fixes all deprecations (including python 3.6 deprecations) encountered in the test suite.

However locally I get a lot of

________________ [doctest] docs/ccdproc/reduction_toolbox.rst _________________
_pytest.runner:149: in __init__
    ???
_pytest.runner:137: in <lambda>
    ???
_pytest.vendored_packages.pluggy:724: in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
_pytest.vendored_packages.pluggy:338: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
_pytest.vendored_packages.pluggy:333: in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
_pytest.vendored_packages.pluggy:595: in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
_pytest.vendored_packages.pluggy:253: in _wrapped_call
    return call_outcome.get_result()
_pytest.vendored_packages.pluggy:278: in get_result
    raise ex[1].with_traceback(ex[2])
_pytest.vendored_packages.pluggy:264: in __init__
    self.result = func()
_pytest.vendored_packages.pluggy:596: in execute
    res = hook_impl.function(*args)
_pytest.runner:90: in pytest_runtest_call
    ???
C:\...\lib\site-packages\astropy-2.0.dev17912-py3.5-win-amd64.egg\astropy\tests\pytest_plugins.py:204: in runtest
    raise_on_error=True, verbose=False, encoding='utf-8')
C:\...\lib\doctest.py:2065: in testfile
    runner.run(test)
C:\...\lib\doctest.py:1830: in run
    r = DocTestRunner.run(self, test, compileflags, out, False)
C:\...\lib\doctest.py:1453: in run
    self.debugger = _OutputRedirectingPdb(save_stdout)
C:\...\lib\doctest.py:357: in __init__
    pdb.Pdb.__init__(self, stdout=out, nosigint=True)
C:\...\lib\pdb.py:153: in __init__
    import readline
C:\...\lib\site-packages\readline.py:34: in <module>
    rl = Readline()
C:\...\lib\site-packages\pyreadline\rlmain.py:422: in __init__
    BaseReadline.__init__(self)
C:\...\lib\site-packages\pyreadline\rlmain.py:65: in __init__
    self.read_inputrc()
C:\...\lib\site-packages\pyreadline\rlmain.py:404: in read_inputrc
    if os.path.isfile(inputrcpath):
C:\...\lib\genericpath.py:30: in isfile
    st = os.stat(path)
E   DeprecationWarning: The Windows bytes API has been deprecated, use Unicode filenames instead

So while it's (probably) good to fix the deprecations I personally wouldn't want that setting to be activated by default.

[MSeifert04]

I undid the enable_deprecations_as_exceptions option again. It's really annoying to have all these failures locally. 😄 Is it possible to "activate" it on a test-basis rather than as config? Something like using python setup.py test --deprecations?

[mwcraig]

I don't know that there is a command line option for it...could see it being handy, though.

Ottherwise, the changes look good.

[mwcraig]

I think this is ready to go, feel free to merge at will. The only I haven't yet is to make sure there are not additional rebases required for some of the other open PRs.

[bsipocz]

@MSeifert04 - I'm sure you can propose something like --deprecations to the testing mechanism that will simply override the enable_deprecations_as_exceptions option from the config file.

[MSeifert04]

@bsipocz Is that astropy, astropy-helpers or should that rather be a seperate pytest plugin package (as I understand there's some effort to split them out of astropy)?

[crawfordsm]

Merging, and I'd suggest adding an issue int he appropriate place about the deprecations.

[bsipocz]

@MSeifert04 - At the moment the testing lives in astropy core. You're right that there are plans to move everything out in a separate package, but that shouldn't be a show stopper for any enhancement, as it may or may not happen during the summer.