Git DataSource sync fails when HTTP proxies are configured

[vrelk-net]

NetBox version

v3.5.0

Python version

3.8

Steps to Reproduce

1. Configure HTTP_PROXIES in configuration.py
2. Run a Git based Data Source sync

HTTP_PROXIES = {
    'http': 'http://xxx.xxx.xxx.xxx:3128',
    'https': 'http://xxx.xxx.xxx.xxx:3128',
}

Expected Behavior

If you have HTTP_PROXIES configured, the sync task fails. If you comment out that section of the config, then restart the netbox-rq service, the sync works.

Observed Behavior

May  4 12:39:20 it-netbox python3[141419]: 12:39:20 default: core.jobs.sync_datasource(job=<Job: 54fd9fa1-a5b8-49de-ae4f-6a2288d2fd50>) (54fd9fa1-a5b8-49de-ae4f-6a2288d2fd50)
May  4 12:39:21 it-netbox python3[236504]: 12:39:21 [Job 54fd9fa1-a5b8-49de-ae4f-6a2288d2fd50]: exception raised while executing (core.jobs.sync_datasource)
May  4 12:39:21 it-netbox python3[236504]: Traceback (most recent call last):
May  4 12:39:21 it-netbox python3[236504]:   File "/opt/netbox/venv/lib/python3.8/site-packages/rq/worker.py", line 1359, in perform_job
May  4 12:39:21 it-netbox python3[236504]:     rv = job.perform()
May  4 12:39:21 it-netbox python3[236504]:   File "/opt/netbox/venv/lib/python3.8/site-packages/rq/job.py", line 1178, in perform
May  4 12:39:21 it-netbox python3[236504]:     self._result = self._execute()
May  4 12:39:21 it-netbox python3[236504]:   File "/opt/netbox/venv/lib/python3.8/site-packages/rq/job.py", line 1215, in _execute
May  4 12:39:21 it-netbox python3[236504]:     result = self.func(*self.args, **self.kwargs)
May  4 12:39:21 it-netbox python3[236504]:   File "/opt/netbox-3.5.0/netbox/core/jobs.py", line 33, in sync_datasource
May  4 12:39:21 it-netbox python3[236504]:     raise e
May  4 12:39:21 it-netbox python3[236504]:   File "/opt/netbox-3.5.0/netbox/core/jobs.py", line 20, in sync_datasource
May  4 12:39:21 it-netbox python3[236504]:     datasource.sync()
May  4 12:39:21 it-netbox python3[236504]:   File "/opt/netbox-3.5.0/netbox/core/models/data.py", line 155, in sync
May  4 12:39:21 it-netbox python3[236504]:     with backend.fetch() as local_path:
May  4 12:39:21 it-netbox python3[236504]:   File "/usr/lib/python3.8/contextlib.py", line 113, in __enter__
May  4 12:39:21 it-netbox python3[236504]:     return next(self.gen)
May  4 12:39:21 it-netbox python3[236504]:   File "/opt/netbox-3.5.0/netbox/core/data_backends.py", line 99, in fetch
May  4 12:39:21 it-netbox python3[236504]:     config.set("http", "proxy", proxy)
May  4 12:39:21 it-netbox python3[236504]:   File "/opt/netbox/venv/lib/python3.8/site-packages/dulwich/config.py", line 735, in set
May  4 12:39:21 it-netbox python3[236504]:     return self.writable.set(section, name, value)
May  4 12:39:21 it-netbox python3[236504]: NotImplementedError: <bound method StackedConfig.set of <StackedConfig for []>>