Fix image handling

See merge request !1

When not encoded ended up with
``` self['oauth_body_hash'] = base64.b64encode(sha1(self.body).digest())
   TypeError: Unicode-objects must be encoded before hashing
   ```

Changes includes:
* Fix syntax error `ImportError, e` as `ImportError as e`.
* `urllib.quote` -> `urllib.parse`.
* Fix `print` syntax error.
* `StringIO` -> `io import StringIO`.

This is a fork from https://github.com/uw-it-aca/spotseeker_client.
Updated to Django 2.x - this is the only change from upstream in this commit.
Now compatible with Python 3.x and Django 2.x