Restore COPY ... TO STDOUT behavior in cqlsh

Patch by brandonwilliams; reviewed by adelapena for CASSANDRA-18353

CHANGES.txt

@@ -1,4 +1,5 @@
 4.1.2
+ * Fix COPY ... TO STDOUT behavior in cqlsh (CASSANDRA-18353)
  * Remove six and Py2SaferScanner merge cruft (CASSANDRA-18354)
  
 

pylib/cqlshlib/copyutil.py

@@ -86,6 +86,11 @@ def printmsg(msg, eol='\n'):
     sys.stdout.flush()
 
 
+# Keep arguments in sync with printmsg
+def swallowmsg(msg, eol='\n'):
+    None
+
+
 class OneWayPipe(object):
     """
     A one way pipe protected by two process level locks, one for reading and one for writing.
@@ -249,7 +254,7 @@ class CopyTask(object):
             DEBUG = True
 
         # do not display messages when exporting to STDOUT unless --debug is set
-        self.printmsg = printmsg if self.fname is not None or direction == 'from' or DEBUG else None
+        self.printmsg = printmsg if self.fname is not None or direction == 'from' or DEBUG else swallowmsg
         self.options = self.parse_options(opts, direction)
 
         self.num_processes = self.options.copy['numprocesses']