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.
shadowsocks-libev doesn't support connecting through an upstream HTTP
proxy, so if the test environment requires that then there's nothing we can
do. (In future it might be possible to set up a local server to avoid this
problem.)