slapproxy: Teach slapproxy to handle non-ascii instance parameters

1. when forming instance parameters xml dict on client side, we cannot
   use str() to convert parameter_value to string - because it breaks e.g.
   this way:

   In [1]: s = u'Привет Мир!'
   In [2]: str(s)
   ---------------------------------------------------------------------------
   UnicodeEncodeError                        Traceback (most recent call

   UnicodeEncodeError: 'ascii' codec can't encode characters in position
   0-5: ordinal not in range(128)

   Fix is: convert arguments to unicode strings.

2. when decoding xml on server side it was erroneously assumed to be
   always unicode, and this way xml.encode('utf-8') fails if xml is str
   but with non-ascii characters:

   In [3]: r = 'hello world'

   In [4]: r.encode('utf-8')
   Out[4]: 'hello world'

   In [5]: t = s.encode('utf-8')

   In [6]: t
   Out[6]: '\xd0\x9f\xd1\x80\xd0\xb8\xd0\xb2\xd0\xb5\xd1\x82 \xd0\x9c\xd0\xb8\xd1\x80!'

   In [7]: t.encode('utf-8')
   ---------------------------------------------------------------------------
   UnicodeDecodeError                        Traceback (most recent call last)

   UnicodeDecodeError: 'ascii' codec can't decode byte 0xd0 in position 0: ordinal not in range(128)

   Fix is: don't assume xml string is unicode and decode it only, if it
           is unicode, and leave as it is if it is just str.

slapos/proxy/views.py

@@ -50,10 +50,19 @@ class UnauthorizedError(Exception):
   pass
 
 
+# cast everything to string, utf-8 encoded
+def to_str(v):
+  if isinstance(v, str):
+    return v
+  if not isinstance(v, unicode):
+    v = unicode(v)
+  return v.encode('utf-8')
+
+
 def xml2dict(xml):
   result_dict = {}
   if xml is not None and xml != '':
-    tree = etree.fromstring(xml.encode('utf-8'))
+    tree = etree.fromstring(to_str(xml))
     for element in tree.iter(tag=etree.Element):
       if element.tag == 'parameter':
         key = element.get('id')
@@ -70,7 +79,7 @@ def dict2xml(dictionary):
   instance = etree.Element('instance')
   for parameter_id, parameter_value in dictionary.iteritems():
     # cast everything to string
-    parameter_value = str(parameter_value)
+    parameter_value = unicode(parameter_value)
     etree.SubElement(instance, "parameter",
                      attrib={'id': parameter_id}).text = parameter_value
   return etree.tostring(instance,

slapos/tests/slapproxy/__init__.py

@@ -463,6 +463,15 @@ class TestRequest(MasterMixin):
         self.request('http://sr//', None, 'MyFirstInstance', 'slappart2').__dict__,
         self.request('http://sr//', None, 'frontend', 'slappart2').__dict__)
 
+  def test_request_with_nonascii_parameters(self):
+    """
+    Verify that request with non-ascii parameters is correctly accepted
+    """
+    self.add_free_partition(1)
+    request = self.request('http://sr//', None, 'myinstance', 'slappart0',
+                           partition_parameter_kw={'text': u'Привет Мир!'})
+    self.assertIsInstance(request, slapos.slap.ComputerPartition)
+
 
 class TestSlaveRequest(MasterMixin):
   """