Fix for saving TIFF image into an io.BytesIO buffer

[mfergie]

Hi,

When trying to save to a io.BytesIO() I am getting the following error (on python 2.7.8 and 3.4.2):

Traceback (most recent call last):
  File "pillow-tiff-string-buffer.py", line 15, in <module>
    pilim.save(string_buffer, format="tiff", compression='tiff_lzw')
  File "/usr/local/lib/python2.7/site-packages/PIL/Image.py", line 1685, in save
    save_handler(self, fp, filename)
  File "/usr/local/lib/python2.7/site-packages/PIL/TiffImagePlugin.py", line 1127, in _save
    _fp = os.dup(fp.fileno())
io.UnsupportedOperation: fileno

The enclosed changes rectify this issue by catching the exception instead of relying on the hasattr test.

I'm not sure where I should create the unit-test, but I have created a minimal gist to reproduce:
https://gist.github.com/mfergie/c3baa78d1c1b1a9a239b

Note, this only happens when specifying compression when saving.

[hugovk]

@mfergie Please can you include tests for this? If there's not already, it'd be good to test both without compression and with different kinds of compression. Check these:

tests/test_file_tiff.py
tests/test_file_libtiff.py

Thanks.

[mfergie]

@hugovk Will look into it this afternoon.

[mfergie]

@hugovk I've added a test here:
https://github.com/mfergie/Pillow/blob/master/Tests/test_file_tiff.py#L329

Could you please check it's suitability? Thanks

[wiredfool]

I want to review this as well.

[wiredfool]

I've made a few minor changes -- hoisted the imports and moved the tests to the test_file_libtiff file, since libtiff is an optional build and that file checks for libtiff in the build.

I also changed the test file to our standard image -- was the F mode image an important part of the test? We should probably do an exhaustive set of tests on all the various formats, but not necessary for this PR.

[wiredfool]

Thanks.

[mfergie]

F mode was not important for the tests. Thanks for your assistance, Martin.