Index: runtime.py
===================================================================
--- runtime.py	(revision 327)
+++ runtime.py	(working copy)
@@ -8,11 +8,12 @@
 
 from mako import exceptions, util
 import inspect, sys
+import copy
 
 class Context(object):
     """provides runtime namespace, output buffer, and various callstacks for templates."""
-    def __init__(self, buffer, **data):
-        self._buffer_stack = [buffer]
+    def __init__(self, **data):
+        self._buffer_stack = []
         self._data = data
         self._kwargs = data.copy()
         self._with_template = None
@@ -33,9 +34,16 @@
         return self._data.keys()
     def __getitem__(self, key):
         return self._data[key]
-    def push_buffer(self):
+    def push_buffer(self, as_unicode=False, output_encoding=None, encoding_errors=None):
         """push a capturing buffer onto this Context."""
-        self._buffer_stack.append(util.FastEncodingBuffer())
+        unicode = 'utf-8', 'utf8', 'unicode'
+        if as_unicode:
+            buf = util.FastEncodingBuffer()
+        elif output_encoding and output_encoding.lower() in unicode:
+            buf = util.FastEncodingBuffer(output_encoding, encoding_errors)
+        else:
+            buf = util.StringIO()
+        self._buffer_stack.append(buf)
     def pop_buffer(self):
         """pop the most recent capturing buffer from this Context."""
         return self._buffer_stack.pop()
@@ -276,13 +284,8 @@
 
 def _render(template, callable_, args, data, as_unicode=False):
     """create a Context and return the string output of the given template and template callable."""
-    if as_unicode:
-        buf = util.FastEncodingBuffer()
-    elif template.output_encoding:
-        buf = util.FastEncodingBuffer(template.output_encoding, template.encoding_errors)
-    else:
-        buf = util.StringIO()
-    context = Context(buf, **data)
+    context = Context(**data)
+    context.push_buffer(as_unicode, template.output_encoding, template.encoding_errors)
     context._with_template = template
     _render_context(template, callable_, context, *args, **_kwargs_for_callable(callable_, data))
     return context.pop_buffer().getvalue()
@@ -294,7 +297,7 @@
         if arg != 'context' and arg in data and arg not in kwargs:
             kwargs[arg] = data[arg]
     return kwargs
-    
+
 def _render_context(tmpl, callable_, context, *args, **kwargs):
     import mako.template as template
     # create polymorphic 'self' namespace for this template with possibly updated context
@@ -306,7 +309,7 @@
         # otherwise, call the actual rendering method specified
         (inherit, lclcontext) = _populate_self_namespace(context, tmpl.parent)
         _exec_template(callable_, context, args=args, kwargs=kwargs)
-        
+
 def _exec_template(callable_, context, args=None, kwargs=None):
     """execute a rendering callable given the callable, a Context, and optional explicit arguments
 
@@ -329,8 +332,9 @@
                 if not result:
                     raise error
             else:
-                context._buffer_stack = [util.StringIO()]
                 error_template = exceptions.html_error_template()
+                while context._buffer_stack: del context._buffer_stack[0]
+                context.push_buffer(False, error_template.output_encoding, error_template.encoding_errors)
                 context._with_template = error_template
                 error_template.render_context(context, error=error)
     else: