Resolve Issue #153: don't wrap GzipFile in contextlib.closing

This is no longer necessary since we dropped support for Python 2.6.
The GzipFile from Py2.7 and above is already a context manager, so the
closing is not required.

https://docs.python.org/2/library/gzip.html

smart_open/smart_open_lib.py

@@ -41,7 +41,6 @@
 
 if IS_PY2:
     import cStringIO as StringIO
-import contextlib
 
 if sys.version_info[0] == 2:
     import httplib
@@ -304,7 +303,7 @@ def _detect_codec(filename):
 
 
 def _wrap_gzip(fileobj, mode):
-    return contextlib.closing(gzip.GzipFile(fileobj=fileobj, mode=mode))
+    return gzip.GzipFile(fileobj=fileobj, mode=mode)
 
 
 def _wrap_none(fileobj, mode):

smart_open/tests/test_s3.py

@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-import contextlib
 import logging
 import gzip
 import io
@@ -131,7 +130,7 @@ def test_read_gzip(self):
         expected = u'раcцветали яблони и груши, поплыли туманы над рекой...'.encode('utf-8')
         buf = io.BytesIO()
         buf.close = lambda: None  # keep buffer open so that we can .getvalue()
-        with contextlib.closing(gzip.GzipFile(fileobj=buf, mode='w')) as zipfile:
+        with gzip.GzipFile(fileobj=buf, mode='w') as zipfile:
             zipfile.write(expected)
         create_bucket_and_key(contents=buf.getvalue())
 
@@ -145,12 +144,12 @@ def test_read_gzip(self):
         # Make sure the buffer we wrote is legitimate gzip.
         #
         sanity_buf = io.BytesIO(buf.getvalue())
-        with contextlib.closing(gzip.GzipFile(fileobj=sanity_buf)) as zipfile:
+        with gzip.GzipFile(fileobj=sanity_buf) as zipfile:
             self.assertEqual(zipfile.read(), expected)
 
         _LOGGER.debug('starting actual test')
         with smart_open.s3.BufferedInputBase('mybucket', 'mykey') as fin:
-            with contextlib.closing(gzip.GzipFile(fileobj=fin)) as zipfile:
+            with gzip.GzipFile(fileobj=fin) as zipfile:
                 actual = zipfile.read()
 
         self.assertEqual(expected, actual)
@@ -261,11 +260,11 @@ def test_gzip(self):
 
         expected = u'а не спеть ли мне песню... о любви'.encode('utf-8')
         with smart_open.s3.BufferedOutputBase('mybucket', 'writekey') as fout:
-            with contextlib.closing(gzip.GzipFile(fileobj=fout, mode='w')) as zipfile:
+            with gzip.GzipFile(fileobj=fout, mode='w') as zipfile:
                 zipfile.write(expected)
 
         with smart_open.s3.BufferedInputBase('mybucket', 'writekey') as fin:
-            with contextlib.closing(gzip.GzipFile(fileobj=fin)) as zipfile:
+            with gzip.GzipFile(fileobj=fin) as zipfile:
                 actual = zipfile.read()
 
         self.assertEqual(expected, actual)