removing a source config causes turku-update-config to error

Removing a source from /etc/turku-agent/sources.d/ causes turku-update-config to error.

After deleting or renaming a .json file to .json.disabled the I get this error:

$ sudo turku-update-config
Traceback (most recent call last):
  File "/usr/bin/turku-update-config", line 20, in <module>
    sys.exit(update_config.main(sys.argv))
  File "/usr/lib/python2.6/dist-packages/turku_agent/update_config.py", line 142, in main
    config = load_config(args.config_dir)
  File "/usr/lib/python2.6/dist-packages/turku_agent/utils.py", line 211, in load_config
    for s in sources_config:
RuntimeError: dictionary changed size during iteration

I discovered this is because it still reads in configs from /var/lib/turku-agent/sources.d/ and then tries changing a dictionary while iterating over it.

Removing the corresponding file from /var/lib/turku-agent/sources.d/ fixes it.