[Build] Prevent usage of twisted>=24

[mhertz]

Breaking ability of adding multiple torrents at once in WebUI, with following error in web-console after pressing 'Add':

deluge-all.js:7 Uncaught TypeError: Cannot read properties of undefined (reading 'filename')
    at S.getFilename (deluge-all.js:7:1946)
    at S.<anonymous> (deluge-all.js:3:2013)
    at Ext.util.MixedCollection.each (ext-all.js:21:111850)
    at constructor.each (ext-all.js:21:321534)
    at S.onAddClick (deluge-all.js:3:1932)
    at S.onClick (ext-all.js:21:426947)
    at HTMLTableElement.I (ext-all.js:21:57750)

The issue stems from only one of the torrents getting uploaded to server, after cgi.parse_multipart was removed from twisted.web.http and replaced with email.message_from_bytes, in there commit 4579398.

Note, there's currently a twisted draft PR replacing email.message* with 'multipart' lib, as seemingly better fitted/faster, and which coincidentally also is fixing our issue.

[cas--]

Can you provide an example of the problem? Why can't we handle this in the web server code?

Edit1: I cannot replicate, however I think there is an issue with adding multiple torrent files in the file picker which would suggest a problem in the frontend js code rather than server side

Edit2: Ah so I wasn't actually switching Twisted to an earlier version so I can see it now

[cas--]

Okay I can see the problem now. The content-disposition of the file upload form is using the same name for both files.

Sample snippet of request

Content-Disposition: form-data; name="file"; filename="test1.torrent"
Content-Type: application/x-bittorrent
...
Content-Disposition: form-data; name="file"; filename="tes2.torrent"
Content-Type: application/x-bittorrent

From mdn web docs there is a suggestion that this is a valid when using the multiple attribute:

When dealing with multiple files in the same field (for example, the multiple attribute of an element), there can be several subparts with the same name.

I think the only fix is to override the _getMultiPartArgs with our own version:

+from collections import defaultdict
 import fnmatch
 import json
 import logging
@@ -40,7 +41,7 @@ def _getMultiPartArgs(content: bytes, ctype: bytes) -> dict[bytes, list[bytes]]:
     """
     Parse the content of a multipart/form-data request.
     """
-    result = {}
+    result = defaultdict(list)
     multiPartHeaders = b'MIME-Version: 1.0\r\n' + b'Content-Type: ' + ctype + b'\r\n'
     msg = message_from_bytes(multiPartHeaders + content)
 
@@ -56,7 +57,7 @@ def _getMultiPartArgs(content: bytes, ctype: bytes) -> dict[bytes, list[bytes]]:
             continue
 
         payload: bytes = part.get_payload(decode=True)  # type:ignore[assignment]
-        result[name.encode('utf8')] = [payload]
+        result[name.encode('utf8')].append(payload)
     return result

Created Twisted Issue/PR: twisted/twisted#12423