built-in debugging is now based on Python logging module

CHANGES.txt

@@ -30,6 +30,7 @@ Revision 4.2.6rc0
   rebuilt on top of these new optimized versions keeping all the legacy
   for compatibility reasons. These classes no more keep references to 
   SnmpEngine what makes them reusable with many SnmpEngine class instances.
+- Built-in debugging is now based on Python logging module.
 - Example on a single Transport Dispatcher use with multiple SnmpEngine's
   in oneliner AsyncCommandGenerator & AsyncNotificationOriginator based
   applicatons added.

pysnmp/debug.py

@@ -1,5 +1,5 @@
-import sys
 import time
+import logging
 from pyasn1.compat.octets import octs2ints
 from pysnmp import error
 from pysnmp import __version__
@@ -31,13 +31,33 @@ flagMap = {
     'all': flagAll
     }
 
+class Printer:
+    def __init__(self, logger=None, handler=None, formatter=None):
+        if logger is None:
+            logger = logging.getLogger('pysnmp')
+        logger.setLevel(logging.DEBUG)
+        if handler is None:
+            handler = logging.StreamHandler()
+        if formatter is None:
+            formatter = logging.Formatter('%(name)s: %(message)s')
+        handler.setFormatter(formatter)
+        handler.setLevel(logging.DEBUG)
+        logger.addHandler(handler)
+        self.__logger = logger
+
+    def __call__(self, msg): self.__logger.debug(msg)
+    def __str__(self): return '<python built-in logging>'
+
 class Debug:
-    defaultPrinter = sys.stderr and sys.stderr.write or None
-    def __init__(self, *flags):
+    defaultPrinter = None
+    def __init__(self, *flags, **options):
         self._flags = flagNone
-        if not self.defaultPrinter:
-            raise error.PySnmpError('Null debug writer specified')
-        self._printer = self.defaultPrinter
+        if options.get('printer') is not None:
+            self._printer = options.get('printer')
+        elif self.defaultPrinter is not None:
+            self._printer = self.defaultPrinter
+        else:
+            self._printer = Printer()
         self('running pysnmp version %s' % __version__)
         for f in flags:
             inverse = f and f[0] in ('!', '~')
@@ -57,7 +77,7 @@ class Debug:
         return 'logger %s, flags %x' % (self._printer, self._flags)
     
     def __call__(self, msg):
-        self._printer('DBG: [%s]: %s\n' % (self.timestamp(), msg))
+        self._printer('[%s]: %s' % (self.timestamp(), msg))
 
     def __and__(self, flag):
         return self._flags & flag