Wokkel imports `_PY3` from swisted.compat, which is not there anymore

[Eugene Crosser]

Python3-wokkel package version 18.0.0-3.1 has this code in the file `data_form.py`:

from twisted.python.compat import iteritems, unicode, _PY3

but symbol `_PY3` is not defined in twisted.compat from the package python3-twisted version 22.1.0-2ubuntu2.3. And obviously it is wrong to import names that start with `_`, so I qualify this as a bug in `wokkel` package.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: python3-wokkel 18.0.0-3.1 [modified: usr/lib/python3/dist-packages/wokkel/data_form.py]
ProcVersionSignature: Ubuntu 5.15.0-67.74-generic 5.15.85
Uname: Linux 5.15.0-67-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.3
Architecture: amd64
CasperMD5CheckResult: unknown
Date: Wed Mar 8 23:37:50 2023
PackageArchitecture: all
SourcePackage: wokkel
UpgradeStatus: Upgraded to jammy on 2022-01-26 (406 days ago)