Add test to reproduce UnicodeDecodeError bug at py27

Hi!

At py27 scripttest try to decode nonvalid utf8 stdout of script to utf8 and failed with UnicodeDecodeError.
I add test to reproduce this bug.

I run this test at py27 and py33 with
```
tox -e py27,py33
```
At py27 failed
At py33 succeed