add test demonstrating issue 37

Author: williballenthin

tests/data/dns_log_malformed.evtx

@@ -3,3 +3,7 @@ The source for system.evtx with md5 182de19fe6a25b928a34ad59af0bbf1e
 
 The source for security.evtx with md5 8fa20a376cb6745453bc51f906e0fcd0
  was Carlos Dias, via email, on May 4, 2017.
+
+The source for ae831beda7dfda43f4de0e18a1035f64/dns_log_malformed.evtx
+ was @stephensheridan, via Github issue #37 (https://github.com/williballenthin/python-evtx/issues/37).
+

tests/data/readme.md

@@ -66,3 +66,17 @@ def security():
         with contextlib.closing(mmap.mmap(f.fileno(), 0,
                                           access=mmap.ACCESS_READ)) as buf:
             yield buf
+
+
+@pytest.fixture
+def data_path():
+    '''
+    fetch the file system path of the directory containing test files.
+
+    Returns:
+      str: the file system path of the test directory.
+    '''
+    cd = os.path.dirname(__file__)
+    datadir = os.path.join(cd, 'data')
+    return datadir
+

tests/fixtures.py

@@ -0,0 +1,16 @@
+import Evtx.Evtx as evtx
+
+from fixtures import *
+
+
+def test_render_records(data_path):
+    '''
+    regression test demonstrating issue 37.
+
+    Args:
+      data_path (str): the file system path of the test directory.
+    '''
+    with evtx.Evtx(os.path.join(data_path, 'dns_log_malformed.evtx')) as log:
+        for chunk in log.chunks():
+            for record in chunk.records():
+                assert record.xml() is not None