Currently the test script assumes the returned web page is always encoded in UTF-8, which might not be the case. It is likely that the real encoding is `ISO-8859-1` and that running the script under python3 will raise error:
```
<
{ [11931 bytes data]
100 11923 0 11923 0 0 184k 0 --:--:-- --:--:-- --:--:-- 187k
Traceback (most recent call last):
File "tests/test.py", line 106, in <module>
line = str(line, 'utf8')
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xa0 in position 1105: invalid start byte
```
This pull request makes no assumption on the returned data and send the raw output to stderr as `bytes`. This should allow the test script to finish successfully when `tests/test.py` is run by python3.