More flexible logging support

Use customized StreamHandler from Python logging module to print
only messages for the specified loglevel to the console.

mininet/logging_mod.py

+# Since StreamHandler automatically adds newlines, define a mod to more easily
+# support interactive mode when we want it, or errors-only logging for running
+# unit tests.
+
+from logging import StreamHandler
+import types
+
+# Modified from python2.5/__init__.py to not require newlines
+class StreamHandlerNoNewline(StreamHandler):
+
+    def emit(self, record):
+        """
+        Emit a record.
+
+        If a formatter is specified, it is used to format the record.
+        The record is then written to the stream with a trailing newline
+        [N.B. this may be removed depending on feedback]. If exception
+        information is present, it is formatted using
+        traceback.print_exception and appended to the stream.
+        """
+        try:
+            msg = self.format(record)
+            fs = "%s" # was "%s\n"
+            if not hasattr(types, "UnicodeType"): #if no unicode support...
+                self.stream.write(fs % msg)
+            else:
+                try:
+                    self.stream.write(fs % msg)
+                except UnicodeError:
+                    self.stream.write(fs % msg.encode("UTF-8"))
+            self.flush()
+        except (KeyboardInterrupt, SystemExit):
+            raise
+        except:
+            self.handleError(record)
\ No newline at end of file