SDWriter.close() fails when the underlying stream has an error

[greglandrum]

Here's a python3 example. The stream error is caused by another problem that still needs to be tracked down:

In [1]: from rdkit import Chem

In [2]: import gzip

In [3]: m = Chem.MolFromSmiles('C')

In [4]: f = gzip.open('/tmp/out.sdf.gz','wb+')

In [5]: w = Chem.SDWriter(f)

In [6]: w.write(m)

In [7]: w.flush()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-7-bc2f85e59f78> in <module>()
----> 1 w.flush()

/home/glandrum/anaconda/envs/py34/lib/python3.4/gzip.py in write(self, data)
    341         if len(data) > 0:
    342             self.size = self.size + len(data)
--> 343             self.crc = zlib.crc32(data, self.crc) & 0xffffffff
    344             self.fileobj.write( self.compress.compress(data) )
    345             self.offset += len(data)

TypeError: 'str' does not support the buffer interface

In [8]: w.close()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-8-cae8a84f7881> in <module>()
----> 1 w.close()

/home/glandrum/anaconda/envs/py34/lib/python3.4/gzip.py in write(self, data)
    341         if len(data) > 0:
    342             self.size = self.size + len(data)
--> 343             self.crc = zlib.crc32(data, self.crc) & 0xffffffff
    344             self.fileobj.write( self.compress.compress(data) )
    345             self.offset += len(data)

TypeError: 'str' does not support the buffer interface

In [9]: w=None
terminate called after throwing an instance of 'boost::python::error_already_set'
Aborted (core dumped)