add read mode for dxpy

[ying-w]

Now that dxpy supports non-utf8 read modes, pass 'rb' through

make lint doesn't work tho:

Warning, treated as error:
failed to reach any of the inventories with the following issues:
intersphinx inventory 'http://docs.python.org/3/objects.inv' not fetchable due to <class 'requests.exceptions.ConnectionError'>: HTTPConnectionPool(host='docs.python.org', port=80): Max retries exceeded with url: /3/objects.inv (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x107478d50>: Failed to establish a new connection: [Errno 60] Operation timed out'))

[anujkumar93]

If the intention is to use with stor.Path('dx://path/to/file).open(mode='rb') to access dx files, this is not really necessary because mode is already set in the self object by this point. You can remove it from dx.py, s3.py and swift.py as well. You'd just do in dx.py:

def read_object(self):
    ....
    file_handler = dxpy.DXFile(dxid=self.canonical_resource, project=self.canonical_project, mode=self.mode)
    ....
    if self.mode == 'r':
        ....

If there was some other reasoning behind this, you can disregard my comment.

[ying-w]

Thanks for the feedback. I just realized that OBSFile defined mode i was looking for it in OBSPath instead and not finding it so I dont think the self.mode in your example would work

I'll make the change but I'm not really sure about when when to use open() vs read_object()

[jtratner]

I think that the correct answer is to just not decode? Probably just need to review this again - good point...