[FTB] UnicodeDecoderError thrown when matching non-ascii logs against unicode signatures

Following seen during fuzzing:

---CUT---
    cache_sig_file, cache_metadata = collector.search(crash_info)
  File "/usr/local/lib/python2.7/dist-packages/Reporter/Reporter.py", line 58, in decorator
    return wrapped(self, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/Collector/Collector.py", line 183, in search
    if crashSig.matches(crashInfo):
  File "/usr/local/lib/python2.7/dist-packages/FTB/Signatures/CrashSignature.py", line 104, in matches
    if not symptom.matches(crashInfo):
  File "/usr/local/lib/python2.7/dist-packages/FTB/Signatures/Symptom.py", line 128, in matches
    if self.output.matches(line):
  File "/usr/local/lib/python2.7/dist-packages/FTB/Signatures/Matchers.py", line 67, in matches
    return self.value in val
UnicodeDecodeError: 'ascii' codec can't decode byte 0xa6 in position 215: ordinal not in range(128)

I've got it down to a test that reproduces it:

# encoding=utf-8
class SignatureNonAsciiInStderr(unittest.TestCase):
    def runTest(self):
        config = ProgramConfiguration("test", "x86-64", "linux")
        log = [b"\xA6\n"]
        testSig = CrashSignature('''{
                "symptoms": [
                {
                    "type": "output",
                    "value": "ä"
                }
            ]
        }''')
        crashInfoPos = CrashInfo.fromRawCrashData([], [], config, auxCrashData=log)

        # Check that this doesn't match
        self.assertFalse(testSig.matches(crashInfoPos))

I think the right thing to do is force logs to be Unicode on submission. Doing .decode("cp437") on the log line makes the test pass. Logs should be textual, and if they can't be represented as Unicode, it should be up the reporter to ignore those errors. FuzzManager should also enforce the type that it expects.

Start with FTB/Signatures/Matchers.py and trace the log path through Symptom.py, CrashSignature.py, and CrashInfo.fromRawCrashData as shown in the traceback. Run the inline SignatureNonAsciiInStderr reproduction first. Done means matching non-ASCII signatures against non-ASCII log bytes no longer raises UnicodeDecodeError and the provided case remains unmatched.