Merge branch 'master' into python3

Conflicts:
	wrw/sp/cons.py
	wrw/sp/xhtml.py

diff --cc wrw/sp/cons.py
index c4d9999,4052dce..205de03
--- 1/wrw/sp/cons.py
--- 2/wrw/sp/cons.py
+++ b/wrw/sp/cons.py
@@@ -59,7 -60,8 +59,8 @@@ class context(object)
          node.children.append(self.nodefrom(child))
  
      def addattr(self, node, k, v):
-         node.attrs[str(k)] = str(v)
+         if v is not None:
 -            node.attrs[unicode(k)] = unicode(v)
++            node.attrs[str(k)] = str(v)
  
  class constructor(object):
      def __init__(self, ns, elcls=element, ctx=None):

diff --cc wrw/sp/xhtml.py
index 5f1ca45,f10d315..50c70b6
--- 1/wrw/sp/xhtml.py
--- 2/wrw/sp/xhtml.py
+++ b/wrw/sp/xhtml.py
@@@ -15,11 -15,11 +15,11 @@@ class htmlelement(_cons.element)
          return doc
  
  class xhtmlcontext(_cons.context):
 -    attrmap = {u"klass": u"class"}
 +    attrmap = {"klass": "class"}
  
      def addattr(self, node, k, v):
 -        k = unicode(k)
 -        super(xhtmlcontext, self).addattr(node, self.attrmap.get(k, k), v)
 +        k = str(k)
-         node.attrs[self.attrmap.get(k, k)] = str(v)
++        super().addattr(node, self.attrmap.get(k, k), v)
  
  def cons(ctx=None):
      if ctx is None: ctx = xhtmlcontext()