[CrashManager] Setting "value" of "testcase" type field to "53-2" throws a stacktrace

Setting a bucket with the following signature:

{
  "symptoms": [
    {
      "src": "stderr", 
      "type": "output", 
      "value": "/\\[Non\\-crash bug\\] Mismatch on stdout/"
    }, 
    {
      "type": "testcase", 
      "value": "53-2"
    }
  ]
}

causes this stacktrace in FuzzManager:

Traceback:

File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/exception.py" in inner
  41.             response = get_response(request)

File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in _legacy_get_response
  249.             response = self._get_response(request)

File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in _get_response
  187.                 response = self.process_exception_by_middleware(e, request)

File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in _get_response
  185.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/usr/local/lib/python2.7/dist-packages/django/contrib/auth/decorators.py" in _wrapped_view
  23.                 return view_func(request, *args, **kwargs)

File "./crashmanager/views.py" in newSignature
  609.         return __handleSignaturePost(request, bucket)

File "./crashmanager/views.py" in __handleSignaturePost
  563.                                                              requiredOutputSources=requiredOutputs))

File "/srv/fuzzmanager.fuzzing.mozilla.org/FuzzManager/FTB/Signatures/CrashSignature.py" in matches
  104.             if not symptom.matches(crashInfo):

File "/srv/fuzzmanager.fuzzing.mozilla.org/FuzzManager/FTB/Signatures/Symptom.py" in matches
  279.             if self.output.matches(line):

File "/srv/fuzzmanager.fuzzing.mozilla.org/FuzzManager/FTB/Signatures/Matchers.py" in matches
  67.             return self.value in val

Exception Type: UnicodeDecodeError at /crashmanager/signatures/new/
Exception Value: 'ascii' codec can't decode byte 0xe3 in position 7: ordinal not in range(128)

Instead of 53-2 which fails, I can set to /53-2/, which works.

Reproduce the signature submission at crashmanager/views.py in newSignature and follow the stack trace through FTB/Signatures/Symptom.py and FTB/Signatures/Matchers.py. Verify that a testcase value of "53-2" no longer raises UnicodeDecodeError, while the slash-wrapped form continues to work.