https://bitbucket.org/nikratio/s3ql/issues/190/sq3l-should-not-rely-on-xmlns-declarations
https://bitbucket.org/nikratio/s3ql/pull-requests/5/s3c-be-more-lenient-about-xml-namespaces

--- s3ql-2.14/src/s3ql/backends/s3c.py	2015-07-20 19:41:07.000000000 -0700
+++ s3ql-2.14/src/s3ql/backends/s3c.py	2016-01-21 22:41:33.000000000 -0800
@@ -126,6 +126,15 @@
         conn.timeout = int(self.options.get('tcp-timeout', 20))
         return conn
 
+    @staticmethod
+    def _tag_xmlns_uri(elem):
+        '''Extract the XML namespace (xmlns) URI from an element'''
+        if elem.tag[0] == '{':
+            uri, ignore, tag = elem.tag[1:].partition("}")
+        else:
+            uri = None
+        return uri
+
     # This method is also used implicitly for the retry handling of
     # `gs.Backend._get_access_token`. When modifying this method, do not forget
     # to check if this makes it unsuitable for use by `_get_access_token` (in
@@ -215,7 +224,6 @@
         keys_remaining = True
         marker = self.prefix + start_after
         prefix = self.prefix + prefix
-        ns_p = self.xml_ns_prefix
 
         while keys_remaining:
             log.debug('requesting with marker=%s', marker)
@@ -232,16 +240,27 @@
             try:
                 itree = iter(ElementTree.iterparse(self.conn, events=("start", "end")))
                 (event, root) = next(itree)
+                
+                root_xmlns_uri = self._tag_xmlns_uri(root)
+                if root_xmlns_uri is None:
+                    root_xmlns_prefix = ''
+                else:
+                    # Validate the XML namespace
+                    root_xmlns_prefix = '{%s}' % (root_xmlns_uri, )
+                    if root_xmlns_prefix != self.xml_ns_prefix:
+                        log.error('Unexpected server reply to list operation:\n%s',
+                                  self._dump_response(resp, body=None))
+                        raise RuntimeError('List response has %s as root tag, unknown namespace' % root.tag)
 
                 for (event, el) in itree:
                     if event != 'end':
                         continue
 
-                    if el.tag == ns_p + 'IsTruncated':
+                    if el.tag == root_xmlns_prefix + 'IsTruncated':
                         keys_remaining = (el.text == 'true')
 
-                    elif el.tag == ns_p + 'Contents':
-                        marker = el.findtext(ns_p + 'Key')
+                    elif el.tag == root_xmlns_prefix + 'Contents':
+                        marker = el.findtext(root_xmlns_prefix + 'Key')
                         yield marker[len(self.prefix):]
                         root.clear()
 
@@ -404,9 +423,12 @@
             return
         body = self.conn.readall()
         root = self._parse_xml_response(resp, body)
-        if root.tag == self.xml_ns_prefix + 'CopyObjectResult':
+
+        # Some S3 implemenentations do not have a namespace on
+        # CopyObjectResult.
+        if root.tag in [self.xml_ns_prefix + 'CopyObjectResult', 'CopyObjectResult']:
             return
-        elif root.tag == 'Error':
+        elif root.tag in [self.xml_ns_prefix + 'Error', 'Error']:
             raise get_S3Error(root.findtext('Code'), root.findtext('Message'),
                               resp.headers)
         else: