error_log template on Zope2 causes chameleon.exc.ExpressionError: invalid syntax

Trying to view the 'error_log' object on Zope2 (tested on Zope 2.12) results in the error (full traceback at the end):

   - Warning: Compilation failed
   - Warning: chameleon.exc.ExpressionError: invalid syntax

 - String: "len(value) < 70 and value or value[:70] + '...'"
 - Filename: manage_main
 - Location: (88:27)

It's not obvious why the template in question is broken. The lines concerned by the error have this text

    <span tal:define="value entry/value"
      tal:content="python: len(value) &lt; 70 and value or value[:70] + '...'">

Which seem properly escaped.

A test for this error has been committed to the five.pt SVN repo.

The full traceback is:

Traceback (most recent call last):
  [...]
  File "Zope2-2.12.19-py2.6-linux-x86_64.egg/Shared/DC/Scripts/Bindings.py", line 324, in __call__
    return self._bindAndExec(args, kw, None)
  File "Zope2-2.12.19-py2.6-linux-x86_64.egg/Shared/DC/Scripts/Bindings.py", line 361, in _bindAndExec
    return self._exec(bound_data, args, kw)
  File "Zope2-2.12.19-py2.6-linux-x86_64.egg/Products/PageTemplates/PageTemplateFile.py", line 130, in _exec
    return self.pt_render(extra_context=bound_names)
  File "Zope2-2.12.19-py2.6-linux-x86_64.egg/Products/PageTemplates/PageTemplate.py", line 80, in pt_render
    showtal=showtal)
  File "zope.pagetemplate-3.5.2-py2.6.egg/zope/pagetemplate/pagetemplate.py", line 107, in pt_render
    raise PTRuntimeError(str(self._v_errors))
   - Warning: Compilation failed
   - Warning: chameleon.exc.ExpressionError: invalid syntax

 - String: "len(value) < 70 and value or value[:70] + '...'"
 - Filename: manage_main
 - Location: (88:27)
PTRuntimeError: ['Compilation failed', u'chameleon.exc.ExpressionError: invalid syntax\n\n - String: "len(value) < 70 and value or value[:70] + \'...\'"\n - Filename: manage_main\n - Location: (88:27)']