logcat_parsing: Replace errors when decoding logcat output

Some devices print non standard characters to logcat. If an error
occurs when parsing the output, replace the offending character instead
of raising an error.

wa/workloads/speedometer/__init__.py

@@ -20,6 +20,7 @@ from wa.framework.exception import ValidationError, WorkloadError
 from wa.utils.types import list_of_strs
 from wa.utils.misc import unique
 
+
 class Speedometer(ApkUiautoWorkload):
 
     name = 'speedometer'
@@ -55,7 +56,7 @@ class Speedometer(ApkUiautoWorkload):
         super(Speedometer, self).update_output(context)
         result = None
         logcat_file = context.get_artifact_path('logcat')
-        with open(logcat_file) as fh:
+        with open(logcat_file, errors='replace') as fh:
             for line in fh:
                 match = self.regex.search(line)
                 if match:
@@ -65,4 +66,3 @@ class Speedometer(ApkUiautoWorkload):
             context.add_metric('Speedometer Score', result, 'Runs per minute', lower_is_better=False)
         else:
             raise WorkloadError("The Speedometer workload has failed. No score was obtainable.")
-