Previously it was silently ignored, which is dangerous when multiple instances of Radicale are running.
A configuration option to disable locking was added.
* Check the configuration file for errors (check option names and basic type checking).
* Perform basic type checking on command line arguments.
* Only print stack traces in debug mode.
* Include much more information in error messages (e.g. include the path of invalid files).
* Send Bad Request to clients for invalid XML requests or iCalendar data.
* Change the log level of some messages.
* Move parsing/serialization of XML requests/responses from ``xmlutils.py`` to ``__init__.py``.
* Log XML requests/responses in pretty-printed form.
* Previously only the responses were logged in readable form. This is useful for debugging.
* The XML documents are only converted for pretty-printing if debugging is enabled (it's expensive)
* Send XML responses in minimized form to clients.
* Add **encoding** attribute to XML declaration in XML response.
* Only decode XML requests once. (Previously they were decoded, encoded and decoded again.)
If a configuration file is passed with a command line argument and the file is not found, Radicale shows a warning and continues with the default configuration.
There is no reason for doing this, Radicale should just fail.
Instead, this PR allows passing an empty string like ``--config ""``. Radicale will use the default configuration in this case, without trying to load the configuration from the common paths. Previously you had to do specify a path that doesn't exist like ``--config /does/not/exist``, which looks a bit ugly and showed a warning message.
Radicale always tries to load the system-wide configuration file. To turn this off, the logging-config option has to be added to all configuration files and command line arguments. It's easier to disable it by default and only add it once to the system-wide config file.
