watchman.checks.storage should write bytes to test-file on Py3

[saily]

Hi, i'm giving django-minio-storage a try and got an exception when storage-check is executed. I'm running Python 3.4.5 and Django 1.10.6.

Traceback (most recent call last):
  File "/Users/daniel/Workspace/my_project/lib/python3.4/site-packages/watchman/decorators.py", line 17, in wrapped
    response = func(*args, **kwargs)
  File "/Users/daniel/Workspace/my_project/lib/python3.4/site-packages/watchman/checks.py", line 63, in _check_storage
    path = default_storage.save(filename, ContentFile(content))
  File "/Users/daniel/Workspace/my_project/lib/python3.4/site-packages/django/core/files/storage.py", line 54, in save
    return self._save(name, content)
  File "/Users/daniel/Workspace/my_project/lib/python3.4/site-packages/minio_storage/storage.py", line 77, in _save
    content_type)
  File "/Users/daniel/Workspace/my_project/lib/python3.4/site-packages/minio/api.py", line 894, in put_object
    current_data, metadata=metadata)
  File "/Users/daniel/Workspace/my_project/lib/python3.4/site-packages/minio/api.py", line 1557, in _do_put_object
    raise ValueError('Input data must be bytes type')
ValueError: Input data must be bytes type

I was able to fix it by using a byte instead of str writing to the dummy file. This should basically work on Python 2.7 - i'd file a PR later.

[mwarkentin]

@saily Thanks for the report - I'm not too familiar w/ Python 3 yet (we're starting to begin the migration though). Happy to get a fix in if you can open a PR though. :)

[mwarkentin]

If you were able to add a test which could confirm that it works on both python 2.7 and 3.x that would be super helpful!

[saily]

Travis will hopefully do so :-)

[saily]

@mwarkentin see: https://travis-ci.org/mwarkentin/django-watchman/builds/215590048