fix(python): invalid URL creation when output_file_prefix didn't end w…

[KunalSin9h]

…ith /

In file upload docs (https://cog.run/http/#file-uploads):

{
    "output_file_prefix": "https://example.com/upload"
}

But in code, we are appending the filename directly into it without / in between. Then this url is used to send PUT request.

cog/python/cog/files.py

Line 17 in e12f237

url = output_file_prefix + os.path.basename(name)

What it caused is 404 not found, since url become like /uploadimage.png.

To fix this, user output_file_prefix need / at the end of url all the time. Hence this will give error when user forgot this.

{
-    "output_file_prefix": "https://example.com/upload",
+   "output_file_prefix": "https://example.com/upload/"
}