Merge pull request #659 from cderici/attach-resource-binary-file

#659

#### Description

The `attach-resource` method on pylibjuju assumes the resource read is plain text, so it borks when it gets a binary file as a resource.

Fixes #654 

#### QA Steps

```sh
tox -e integration -- tests/integration/test_model.py::test_attach_resource
```

#### Notes & Discussion

Author: jujubot

juju/application.py

@@ -441,7 +441,8 @@ def attach_resource(self, resource_name, file_name, file_obj):
 
         headers['Content-Type'] = 'application/octet-stream'
         headers['Content-Length'] = len(data)
-        headers['Content-Sha384'] = hashlib.sha384(bytes(data, 'utf-8')).hexdigest()
+        data_bytes = data if isinstance(data, bytes) else bytes(data, 'utf-8')
+        headers['Content-Sha384'] = hashlib.sha384(data_bytes).hexdigest()
 
         file_name = str(file_name)
         if not file_name.startswith('./'):

tests/integration/test_model.py

@@ -660,6 +660,9 @@ async def test_attach_resource(event_loop):
         with open(str(charm_path / 'test.file')) as f:
             app.attach_resource('file-res', 'test.file', f)
 
+        with open(str(charm_path / 'test.file'), 'rb') as f:
+            app.attach_resource('file-res', 'test.file', f)
+
 
 @base.bootstrapped
 @pytest.mark.asyncio