F merge missing list datatype

Summary

For #151 (closed). Does not fix the actual problem because this is a CloseWon't Fix (or has to be fixed in the crawler) but raises a better error message instead.

Focus

Check that the correct error message is shown.

Test Environment

Unit tests should be sufficient.

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unittests/test_issues.py

@@ -36,4 +36,4 @@ def test_issue_100():
     xml_el = lxml.etree.parse(filename).getroot()
     with raises(TypeError) as exc_info:
         db.common.models._parse_single_xml_element(xml_el)
-    assert "Invalid datatype: List valued properties" in exc_info.value.msg
+    assert "Invalid datatype: List valued properties" in str(exc_info.value)