BUG/TST: importing util.clipboard shouldnt print to stdout (nosetests)

Author: y-p

pandas/util/clipboard.py

@@ -133,12 +133,12 @@ def xselGetClipboard():
     getcb = macGetClipboard
     setcb = macSetClipboard
 elif os.name == 'posix' or platform.system() == 'Linux':
-    xclipExists = os.system('which xclip') == 0
+    xclipExists = os.system('which xclip > /dev/null') == 0
     if xclipExists:
         getcb = xclipGetClipboard
         setcb = xclipSetClipboard
     else:
-        xselExists = os.system('which xsel') == 0
+        xselExists = os.system('which xsel > /dev/null') == 0
         if xselExists:
             getcb = xselGetClipboard
             setcb = xselSetClipboard