[RDY] Avoid crash with LC_ALL=C and unicode filename

[7lb]

Fixes #1450

This fixes the crash, instead displaying an error.

It's not the best option, but it's better than a crash

---

This change is 

[jgkamat]

I think that one of the tests is failing because there's no test for the case you added. I'm not sure if there's a way to trigger this from the test suite, but if you think of one, could you add a unit test for this?

[7lb]

Mmm, I did not notice any failing errors (not more than those that normally fail at least).

I ran tox -e py36 tests/unit/browser/webkit/network/test_filescheme.py and had 25 passing tests.

I modified test_file in test_filescheme.py to use φτωχικὸ as a filename instead of foo, but that will not raise an exception in tox even with LC_ALL=C so I'm not sure what option there are to test this properly, any ideas?

[jgkamat]

Sorry, I was a bit too vauge there, the coverage tests are failing (meaning that coverage dropped on a perfect file) :P.

I actually can't test/verify anything about the webkit crash, I don't have webkit installed. Could you please provide a webkit crash stacktrace for me to look at?

The reason I'm asking is because (like you said) the test:

    def test_file(self, tmpdir):
        filename = tmpdir / 'φτωχικὸ'
        os.environ['LC_ALL'] = "C"
        filename.ensure()
        url = QUrl.fromLocalFile(str(filename))
        req = QNetworkRequest(url)
        handler = filescheme.FileSchemeHandler(win_id=0)
        reply = handler.createRequest(None, req, None)
        assert reply is None

runs the changed code for me fine, without a patch. I'm not sure if setting the env var in python is sufficient or not (or if I need to be running all of qb, not just the test environment). A stacktrace would help with that :)

[7lb]

Here's a stacktrace, it's actually the same as that in #1450 :)

$ LC_ALL=C python -m qutebrowser --temp-basedir --backend webkit xxφτωχικὸ 
21:31:43 ERROR: Error in qutebrowser.browser.webkit.network.networkmanager.NetworkManager.createRequest
Traceback (most recent call last):
  File "/home/l/.proj/qutebrowser/qutebrowser/utils/utils.py", line 635, in wrapper
    return func(*args, **kwargs)
  File "/home/l/.proj/qutebrowser/qutebrowser/browser/webkit/network/networkmanager.py", line 390, in createRequest
    op, req, outgoing_data)
  File "/home/l/.proj/qutebrowser/qutebrowser/browser/webkit/network/filescheme.py", line 130, in createRequest
    if os.path.isdir(path):
  File "/usr/lib/python3.6/genericpath.py", line 42, in isdir
    st = os.stat(s)
UnicodeEncodeError: 'ascii' codec can't encode characters in position 28-72: ordinal not in range(128)

In any case yeah, I hadn't thought about coverage, in that case adding a tests for an unicode filename is useful even if, de facto, it doesn't work

[7lb]

Actually, I take that back. Since the exception is never raised during tests, those two lines are never tested against.

[The-Compiler]

Looks like @lejar volunteered to write a test in #3177, which would probably catch this too 😉

[7lb]

Great! Feel free to ping me should I need to do more for this PR