Web app can delete file in S3

[robert-clegg-tessella]

Story points: 2

A DELETE request to the Web API (route "deletefile") deletes a single file at the S3 end

Acceptance criteria:
GET request to: http://172.28.129.160:8888/deletefile/{bucket-name}/{relative-path-to-file} (e.g. http://172.28.129.160:8888/deletefile/test-bucket/testdir/testfile.txt)

Should return a warning message if the bucket or the file does not exist at the S3 end

Otherwise, deletes the file and returns a message confirming the deletion

[daniel-hunt-tessella]

Up-to-date Acceptance Criteria
Authorised DELETE request to: http://172.28.129.160:8888/deletefile/
With body of form {"bucket": "<bucket-name>", "file": "<file-path-and-name>"}.
Eg: {"bucket": "ditto-anything-i-want", "file": "/2test2/33testing/444testing/555testing/test.txt"}

Should return a warning message if the bucket or the file does not exist at the S3 end

Otherwise, deletes the file and returns a message confirming the deletion

---

Testing
Note that as part of #71 status and status code errors will be fixed. ✔️
Works for the happy path and if the bucket or file does not exist at the S3 end ✔️

❌ Problem caused when a file path is given that goes outside the bucket - eg {"bucket": "ditto-anything-i-want", "file": ".."}. Also applies when "file": "" is given
This causes a 500 Internal Server Error
This actually happens for all API calls that require a file or directory

2018-11-30 09:47:57,514 ditto-web-api DEBUG    Called delete-file handler
DEBUG:ditto-web-api:Called delete-file handler
2018-11-30 09:47:57,514 ditto-web-api DEBUG    About to check for warning to do with bucket name ditto-anything-i-want
DEBUG:ditto-web-api:About to check for warning to do with bucket name ditto-anything-i-want
2018-11-30 09:47:57,517 ditto-web-api DEBUG    Bucket "ditto-anything-i-want" does exist
DEBUG:ditto-web-api:Bucket "ditto-anything-i-want" does exist
2018-11-30 09:47:57,517 ditto-web-api DEBUG    No bucket related warnings found
DEBUG:ditto-web-api:No bucket related warnings found
ERROR:tornado.application:Uncaught exception DELETE /deletefile/ (172.28.129.1)
HTTPServerRequest(protocol='http', host='172.28.129.160:8888', method='DELETE', uri='/deletefile/', version='HTTP/1.1', remote_ip='172.28.129.1')
Traceback (most recent call last):
  File "/home/vagrant/ditto_web_api/venv/lib64/python3.6/site-packages/tornado/web.py", line 1592, in _execute
    result = yield result
  File "/home/vagrant/ditto_web_api/venv/lib64/python3.6/site-packages/tornado/gen.py", line 1133, in run
    value = future.result()
  File "/home/vagrant/ditto_web_api/venv/lib64/python3.6/site-packages/tornado/gen.py", line 326, in wrapper
    yielded = next(result)
  File "/home/vagrant/ditto_web_api/venv/lib64/python3.6/site-packages/tornado_json/schema.py", line 160, in_wrapper
    output = rh_method(self, *args, **kwargs)
  File "/home/vagrant/ditto_web_api/DittoWebApi/src/handlers/delete_file.py", line 25, in delete
    result = self._data_replication_service.try_delete_file(bucket_name, file_rel_path)
  File "/home/vagrant/ditto_web_api/DittoWebApi/src/services/data_replication/data_replication_service.py", line 92, in try_delete_file
    if not self._external_data_service.does_object_exist(bucket_name, file_rel_path):
  File "/home/vagrant/ditto_web_api/DittoWebApi/src/services/external/external_data_service.py", line 79, indoes_object_exist
    key = bucket.get_key(file_name)
  File "/home/vagrant/ditto_web_api/DittoWebApi/src/services/external/storage_adapters/boto_bucket.py", line13, in get_key
    key = self._bucket.get_key(*args, **kwargs)
  File "/home/vagrant/ditto_web_api/venv/lib64/python3.6/site-packages/boto/s3/bucket.py", line 193, in get_key
    key, resp = self._get_key_internal(key_name, headers, query_args_l)
  File "/home/vagrant/ditto_web_api/venv/lib64/python3.6/site-packages/boto/s3/bucket.py", line 232, in _get_key_internal
    response.status, response.reason, '')
boto.exception.S3ResponseError: S3ResponseError: 400 Bad Request

ERROR:tornado.access:500 DELETE /deletefile/ (172.28.129.1) 61.91ms

[daniel-hunt-tessella]

Problem caused by attempting to delete a file outside of the root directory has been resolved. This now returns a 403 Forbidden error instead of the previous 500 error