Deleting Remote BigWig File Results in Error

Running higlass-server on CentOS7. To replicate:

```
python higlass-server/manage.py ingest_tileset --filename http://127.0.0.1/api/v1/tracks/test.bw --no-upload --filetype bigwig --coordSystem mm10 --uid test
```
Seems to work fine, I can load the file in HiGlass. Running:

```
python higlass-server/manage.py delete_tileset --uuid test
```
Gives the error:
```
Command Error: File does not exist under media root
```
Let me know if you need any more information from me. Thanks in advance!