Use the logging module directly instead of home-grown code.

This has the advantage of overall less custom code; as well as support
for per-module configuration. This would enable a potential solution for
ultrabug#1479, since in the future
it can allow per-module configuration of log levels.

I expect this to mainly help module creators, allowing them to enable
logging for only their module, while disabling all other messages. It
also is easier to use, since the `logging` module's interface is
generally simpler than `self.py3`.

Here, I've made the decision to keep the message format as close as
possible to the existing log messages.

py3status/core.py

@@ -30,6 +30,12 @@
     "info": logging.INFO,
 }
 
+LOGGING_LEVELS = {
+    "error": logging.ERROR,
+    "warning": logging.WARNING,
+    "info": logging.INFO,
+}
+
 DBUS_LEVELS = {"error": "critical", "warning": "normal", "info": "low"}
 
 CONFIG_SPECIAL_SECTIONS = [
@@ -531,27 +537,6 @@ def load_modules(self, modules_list, user_modules):
 
     def _setup_logging(self):
         """Set up the global logger."""
-        log_config = self.config.get("log_config")
-        if log_config:
-            if self.config.get("debug"):
-                self.report_exception("--debug is invalid when --log-config is passed")
-            if self.config.get("log_file"):
-                self.report_exception(
-                    "--log-file is invalid when --log-config is passed"
-                )
-
-            with log_config.open() as f:
-                import logging.config
-
-                try:
-                    config_dict = load(f, strict=False)
-                    logging.config.dictConfig(config_dict)
-                except JSONDecodeError as e:
-                    self.report_exception(str(e))
-            # Nothing else to do. All logging config is provided by the config
-            # dictionary.
-            return
-
         root = logging.getLogger(name=None)
         if self.config.get("debug"):
             root.setLevel(logging.DEBUG)