Introduce custom logger

Implement logger that internally checks if log level is enabled. Thus,
unnecessary log message computation costs are avoid, when logging is
disabled and logging code can be cut in half.

Related pwr-Solaar#2663

lib/solaar/custom_logger.py

@@ -0,0 +1,28 @@
+import logging
+
+
+class CustomLogger(logging.Logger):
+    """Logger, that avoids unnecessary string computations.
+
+    Does not compute messages for disabled log levels.
+    """
+
+    def debug(self, msg, *args, **kwargs):
+        if self.isEnabledFor(logging.DEBUG):
+            super().debug(msg, *args, **kwargs)
+
+    def info(self, msg, *args, **kwargs):
+        if self.isEnabledFor(logging.INFO):
+            super().info(msg, *args, **kwargs)
+
+    def warning(self, msg, *args, **kwargs):
+        if self.isEnabledFor(logging.WARNING):
+            super().warning(msg, *args, **kwargs)
+
+    def error(self, msg, *args, **kwargs):
+        if self.isEnabledFor(logging.ERROR):
+            super().error(msg, *args, **kwargs)
+
+    def critical(self, msg, *args, **kwargs):
+        if self.isEnabledFor(logging.CRITICAL):
+            super().critical(msg, *args, **kwargs)

lib/solaar/gtk.py

@@ -36,7 +36,9 @@
 from solaar import dbus
 from solaar import listener
 from solaar import ui
+from solaar.custom_logger import CustomLogger
 
+logging.setLoggerClass(CustomLogger)
 logger = logging.getLogger(__name__)