[qa] fix unclosed files problems in tests.

tests/io/test_pickle.py

@@ -20,7 +20,8 @@ def test_write_pickled_dict_to_file(tmpdir):
     context.step()
     context.stop()
 
-    assert pickle.loads(fs.open(filename, 'rb').read()) == {'foo': 'bar'}
+    with fs.open(filename, 'rb') as fp:
+        assert pickle.loads(fp.read()) == {'foo': 'bar'}
 
     with pytest.raises(AttributeError):
         getattr(context, 'file')
@@ -28,8 +29,8 @@ def test_write_pickled_dict_to_file(tmpdir):
 
 def test_read_pickled_list_from_file(tmpdir):
     fs, filename = open_fs(tmpdir), 'input.pkl'
-    fs.open(filename,
-            'wb').write(pickle.dumps([['a', 'b', 'c'], ['a foo', 'b foo', 'c foo'], ['a bar', 'b bar', 'c bar']]))
+    with fs.open(filename, 'wb') as fp:
+        fp.write(pickle.dumps([['a', 'b', 'c'], ['a foo', 'b foo', 'c foo'], ['a bar', 'b bar', 'c bar']]))
 
     reader = PickleReader(path=filename)