logger: send warning messages to stderr (#2612)

* logger: send warning messages to stderr

Fix #2561

* logger: filter warnings for stdout

dvc/logger.py

@@ -19,7 +19,7 @@ class LoggingException(Exception):
 
 class ExcludeErrorsFilter(logging.Filter):
     def filter(self, record):
-        return record.levelno < logging.ERROR
+        return record.levelno < logging.WARNING
 
 
 class ColorFormatter(logging.Formatter):
@@ -182,7 +182,7 @@ def setup(level=logging.INFO):
                 },
                 "console_errors": {
                     "class": "dvc.logger.LoggerHandler",
-                    "level": "ERROR",
+                    "level": "WARNING",
                     "formatter": "color",
                     "stream": "ext://sys.stderr",
                 },

tests/unit/test_logger.py

@@ -179,3 +179,10 @@ class TestColorFormatter:
                     logger.info("some info")
                     captured = capsys.readouterr()
                     assert captured.out == ""
+
+
+def test_handlers():
+    stdout, stderr = logger.handlers
+
+    assert stdout.level == logging.DEBUG
+    assert stderr.level == logging.WARNING