BUG/TST: importing util.clipboard shouldnt print to stdout (nosetests)
```
$ nosetests
/usr/bin/xclip   <<<< raise your hand if you've been ignoring this for 6 months
...........
```

`os.system` nastiness. The vbench package has similar problems.

https://github.com/pydata/pandas/pull/3848

:raised_hand: 
