Add XML parser and tests

tests/xml_tests.py

+import unittest
+
+from tornado_aws import xml
+
+
+class TestCase(unittest.TestCase):
+
+    def test_generic_xml(self):
+        expectation = {'test': {'foo': 'bar', 'baz': {'qux': 'corgie'}}}
+        value = """<?xml version="1.0" encoding="UTF-8"?>
+        <test><foo>bar</foo><baz><qux>corgie</qux></baz></test>"""
+        self.assertDictEqual(xml.loads(value), expectation)
+
+    def test_generic_xml_with_attributes(self):
+        expectation = {'test': {'foo': 'bar',
+                                'baz': {'qux': 'corgie', '@val': '1'}}}
+        value = """<?xml version="1.0" encoding="UTF-8"?>
+        <test><foo>bar</foo><baz val="1"><qux>corgie</qux></baz></test>"""
+        self.assertDictEqual(xml.loads(value), expectation)
+
+    def test_generic_xml_with_text_and_children(self):
+        expectation = {'test': {'foo': 'bar',
+                                'baz': {'qux': 'corgie',
+                                        '@val': '1',
+                                        '#text': 'gorge'}}}
+        value = """<?xml version="1.0" encoding="UTF-8"?>
+        <test><foo>bar</foo><baz val="1">gorge<qux>corgie</qux></baz></test>"""
+        self.assertDictEqual(xml.loads(value), expectation)
+
+    def test_invalid_xml(self):
+        with self.assertRaises(ValueError):
+            xml.loads('foo')
+

tornado_aws/xml.py

+"""
+XML Deserialization
+===================
+
+Parse XML return content and return it as a dict.
+
+"""
+from collections import defaultdict
+from xml.etree import ElementTree as etree
+
+
+def loads(content):
+    """Return the XML document returned from AWS as a dict
+
+    :param str content: Response content from AWS
+    :rtype: dict
+    :raises: ValueError
+
+    """
+    try:
+        return _xml_to_dict(etree.XML(content))
+    except etree.ParseError as error:
+        raise ValueError(str(error))
+
+
+def _xml_to_dict(t):
+    """Process child nodes, initially taken from
+    https://stackoverflow.com/a/10076823/13203
+
+    :param xml.etree.ElementTree.Element t: The XML node to process
+
+    """
+    d = {t.tag: {} if t.attrib else None}
+    children = list(t)
+    if children:
+        dd = defaultdict(list)
+        for dc in map(_xml_to_dict, children):
+            for k, v in dc.items():
+                dd[k].append(v)
+        d = {t.tag: {k: v[0] if len(v) == 1 else v for k, v in dd.items()}}
+    if t.attrib:
+        d[t.tag].update(('@' + k, v) for k, v in t.attrib.items())
+    if t.text:
+        text = t.text.strip()
+        if (children or t.attrib) and text:
+            d[t.tag]['#text'] = text
+        else:
+            d[t.tag] = t.text.strip()
+    return dict(d)