TST: Fix UnboundLocalError: local variable 'data' referenced before assignment on Windows

[cgohlke]

Fixes one test error reported at #7055

======================================================================
ERROR: test_wavfile.test_read_early_eof
----------------------------------------------------------------------
Traceback (most recent call last):
  File "X:\Python27-x64\lib\site-packages\nose\case.py", line 197, in runTest
    self.test(*self.arg)
  File "X:\Python27-x64\lib\site-packages\scipy\io\tests\test_wavfile.py", line 91, in test_read_early_eof
    assert_raises(ValueError, wavfile.read, fp, mmap=mmap)
  File "X:\Python27-x64\lib\site-packages\numpy\testing\utils.py", line 1142, in assert_raises
    return nose.tools.assert_raises(*args,**kwargs)
  File "X:\Python27-x64\lib\unittest\case.py", line 473, in assertRaises
    callableObj(*args, **kwargs)
  File "X:\Python27-x64\lib\site-packages\scipy\io\wavfile.py", line 281, in read
    return fs, data
UnboundLocalError: local variable 'data' referenced before assignment

[mp4096]

Cool, thank you! Would've taken me a lot of time to find this bug.

Actually, maybe it would make sense to rewrite these three tests as follows:

def test_read_fail():
    filename = datafile('example_1.nc')
    for mmap in [False, True]:
        assert_raises(ValueError, wavfile.read, filename, mmap=mmap)


def test_read_early_eof():
    filename = datafile('test-44100Hz-le-1ch-4bytes-early-eof.wav')
    for mmap in [False, True]:
        assert_raises(ValueError, wavfile.read, filename, mmap=mmap)


def test_read_incomplete_chunk():
    filename = datafile('test-44100Hz-le-1ch-4bytes-incomplete-chunk.wav')
    for mmap in [False, True]:
        assert_raises(ValueError, wavfile.read, filename, mmap=mmap)

Seems to work properly on my Linux machine.

Rationale: As I've just realised, mmap is overridden if wavfile.read is given a file handle instead of a filename.

[ev-br]

Thanks Christoph!

@mp4096 it probably should test it both ways. I merged this PR as a hotfix, a follow-up PR against master would be welcome, I'd say.

[ev-br]

forward ported in gh-7085