Revert allowing multiple stream handlers; clutters test output

tractor/log.py

@@ -1,6 +1,7 @@
 """
 Log like a forester!
 """
+import sys
 from functools import partial
 import logging
 import colorlog  # type: ignore
@@ -73,6 +74,11 @@ def get_console_log(level: str = None, name: str = None) -> logging.Logger:
         return log
 
     log.setLevel(level.upper() if not isinstance(level, int) else level)
+
+    if not any(
+        handler.stream == sys.stderr for handler in log.handlers
+        if getattr(handler, 'stream', None)
+    ):
         handler = logging.StreamHandler()
         formatter = colorlog.ColoredFormatter(
             LOG_FORMAT,