Download order locations one by one

[madatx]

Hi,

I've tried to use ClientV1.download_order to download all locations at once and got exception:

# ...
File "/usr/local/lib/python3.7/site-packages/planet/api/client.py", line 568, in download_order
  return self._get(locations, models.JSON, callback=callback)
File "/usr/local/lib/python3.7/site-packages/planet/api/client.py", line 61, in _get
  request = self._request(path, body_type, params)
File "/usr/local/lib/python3.7/site-packages/planet/api/client.py", line 52, in _request
  return models.Request(self._url(path), auth or self.auth, params,
File "/usr/local/lib/python3.7/site-packages/planet/api/client.py", line 45, in _url
  if path.startswith('http'):
AttributeError: 'list' object has no attribute 'startswith'

Looks like the problem is that client _get method expects a single location but gets a list instead.

This PR is a possible solution.

[strixcuriosus]

Thanks for the contribution! Your fix looks good to me.

[strixcuriosus]

The build failure is not specific to your branch. I made a separate PR with a fix for these lint and docs errors: #211

[strixcuriosus]

I would recommend adding a test case for the bug you discovered, but the orders methods seem to lack test coverage in general. I've created this issue to add test coverage to the orders related ClientV1 methods #212

[strixcuriosus]

@sarasafavi I see that you've created most of the recent releases. Do you have any concerns about creating a new release to get this orders fix in?

[sarasafavi]

@strixcuriosus the next package release is already lined up and in testing (and will include those text fixes referenced in #211 ), but I can definitely get this fix wrapped into the next next release.

Thank you, @madatx, for finding and fixing this issue!