Failing test_temp_file in cloudpickle_file_test.CloudPickleFileTests

Hello.

I am trying to make RPM package from cloudpickle for Fedora and I found one failing test. `test_temp_file in cloudpickle_file_test.CloudPickleFileTests` is failing during RPM build and also in a virtual environment. I've tested it with Python 3.5 and 3.6.

```
======================================================================
ERROR: test_temp_file (tests.cloudpickle_file_test.CloudPickleFileTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/lbalhar/Software/cloudpickle/tests/cloudpickle_file_test.py", line 96, in test_temp_file
newfile = pickle.loads(cloudpickle.dumps(f))
File "/home/lbalhar/Software/cloudpickle/cloudpickle/cloudpickle.py", line 900, in dumps
cp.dump(obj)
File "/home/lbalhar/Software/cloudpickle/cloudpickle/cloudpickle.py", line 234, in dump
return Pickler.dump(self, obj)
File "/usr/lib64/python3.5/pickle.py", line 408, in dump
self.save(obj)
File "/usr/lib64/python3.5/pickle.py", line 495, in save
rv = reduce(self.proto)
TypeError: cannot serialize '_io.BufferedRandom' object

----------------------------------------------------------------------
Ran 48 tests in 1.698s

FAILED (errors=1)
Test failed:
```
Let me know if I can help you with anything.