mapreduce/multiproc| Puts bad unicode excpetion handling under test

tests/unittest_checker_similar.py

@@ -507,3 +507,29 @@ def test_get_map_data():
         # There doesn't seem to be a faster way of doing this, yet.
         lines = (line for idx, line in lineset_obj.enumerate_stripped())
         assert tuple(expected_lines) == tuple(lines)
+
+
+def test_ammend_stream_bad_unicode():
+    """ Tests that ammend_stream() handles bad unicode errors """
+    sim = similar.SimilarChecker()
+
+    class CustomException(Exception):
+        pass
+
+    class MimicOtherReadError:
+        def readlines(self, *args, **kwargs):  # pylint: disable=no-self-use
+            raise CustomException()
+
+    raised = False
+    try:
+        sim.append_stream("--unimportant-name--", MimicOtherReadError())
+    except CustomException:
+        raised = True
+    assert raised
+
+    class MimicBadUnicode:
+        def readlines(self, *args, **kwargs):  # pylint: disable=no-self-use
+            raise UnicodeDecodeError("a", b"a", 0, 0, "a")
+
+    sim.append_stream("--unimportant-name--", MimicBadUnicode())
+    # nothing should happen that stops us getting here and beyond