[CI] Fix tests stalling/timing out

GitHub pytest runner stalling with the following error:

    [Errno 2] No such file or directory: '/opt/hostedtoolcache/Python/3.10.8/x64/lib/python3.10/site-packages/deluge/plugins'

This is related to the editable install of Deluge via pip

    pip install -e .

and the custom resource_filename in deluge.common is the source of the
problem where a DistInfoDistribution returns a different path to
EggInfoDistribution.

Working egg-info install

    >>> pkg_resources.get_distribution('Deluge')
    deluge 2.1.1.dev8 (/home/user/deluge)

    >>> type(pkg_resources.get_distribution('Deluge'))
    <class 'pkg_resources.EggInfoDistribution'>

    >>> pkg_resources.resource_filename('deluge', 'plugins')
    '/home/user/deluge/deluge/plugins'

This can identified by the `deluge.egg-info` directory in source
directory.

Broken dist-info install

    >>> pkg_resources.get_distribution('Deluge')
    deluge 2.1.1.dev8 (/opt/hostedtoolcache/Python/3.10.8/x64/lib/python3.10/site-packages)

    >>> type(pkg_resources.get_distribution('Deluge'))
    <class 'pkg_resources.DistInfoDistribution'>

    >>> pkg_resources.resource_filename('deluge', 'plugins')
    '/home/user/deluge/deluge/plugins'

This can be worked around by setting an env var that enables legacy mode
but long-term need to replace the custom resource_filename and replace
usage of pkg_resources.

https://setuptools.pypa.io/en/latest/userguide/development_mode.html#legacy-behavior
https://setuptools.pypa.io/en/latest/pkg_resources.html

.github/workflows/ci.yml

@@ -7,6 +7,9 @@ on:
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch:
 
+env:
+  SETUPTOOLS_ENABLE_FEATURES: "legacy-editable"
+
 jobs:
   test-linux:
     runs-on: ubuntu-20.04