templates: disable special mako error handler - ironically this gives better stack traces

Errors in templates could give truncated stack traces pointing at the mako
error handler:

...
File '.../kallithea/kallithea/controllers/files.py', line 202 in index
return render('files/files.html')
File '.../kallithea-venv/lib/python2.7/site-packages/pylons/templating.py', line 244 in render_mako
cache_type=cache_type, cache_expire=cache_expire)
File '.../kallithea-venv/lib/python2.7/site-packages/pylons/templating.py', line 219 in cached_template
return render_func()
File '.../kallithea-venv/lib/python2.7/site-packages/pylons/templating.py', line 241 in render_template
return literal(template.render_unicode(**globs))
File '.../kallithea-venv/lib/python2.7/site-packages/mako/template.py', line 452 in render_unicode
as_unicode=True)
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 803 in _render
**_kwargs_for_callable(callable_, data))
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 835 in _render_context
_exec_template(inherit, lclcontext, args=args, kwargs=kwargs)
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 855 in _exec_template
_render_error(template, context, compat.exception_as())
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 864 in _render_error
result = template.error_handler(context, error)
File '.../kallithea-venv/lib/python2.7/site-packages/pylons/error.py', line 22 in handle_mako_error
raise (exc, None, sys.exc_info()[2])
AttributeError: 'tuple' object has no attribute 'node'

Without the mako error handler we get a full and useful stack trace - including
calls in generated but readable .html.py files.

File '.../kallithea/kallithea/controllers/files.py', line 202 in index
return render('files/files.html')
File '.../kallithea-venv/lib/python2.7/site-packages/pylons/templating.py', line 244 in render_mako
cache_type=cache_type, cache_expire=cache_expire)
File '.../kallithea-venv/lib/python2.7/site-packages/pylons/templating.py', line 219 in cached_template
return render_func()
File '.../kallithea-venv/lib/python2.7/site-packages/pylons/templating.py', line 241 in render_template
return literal(template.render_unicode(**globs))
File '.../kallithea-venv/lib/python2.7/site-packages/mako/template.py', line 452 in render_unicode
as_unicode=True)
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 803 in _render
**_kwargs_for_callable(callable_, data))
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 835 in _render_context
_exec_template(inherit, lclcontext, args=args, kwargs=kwargs)
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 860 in _exec_template
callable_(context, *args, **kwargs)
File '.../data/templates/base/root.html.py', line 219 in render_body
__M_writer(escape(next.body()))
File '.../data/templates/base/base.html.py', line 57 in render_body
__M_writer(escape(next.main()))
File '.../data/templates/files/files.html.py', line 121 in render_main
runtime._include_file(context, u'files_ypjax.html', _template_uri)
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 730 in _include_file
callable_(ctx, **_kwargs_for_include(callable_, context._data, **kwargs))
File '.../data/templates/files/files_ypjax.html.py', line 57 in render_body
runtime._include_file(context, u'files_source.html', _template_uri)
File '.../kallithea-venv/lib/python2.7/site-packages/mako/runtime.py', line 730 in _include_file
callable_(ctx, **_kwargs_for_include(callable_, context._data, **kwargs))
File '.../data/templates/files/files_source.html.py', line 117 in render_body
__M_writer(escape(h.pygmentize_annotation(c.repo_name,c.file,linenos=True,anchorlinenos=True,lineanchors='L',cssclass="code-highlight")))
File '.../kallithea/kallithea/lib/helpers.py', line 360 in pygmentize_annotation
return literal(markup_whitespace(annotate_highlight(filenode, url_func(repo_name), **kwargs)))
File '.../kallithea/kallithea/lib/annotate.py', line 57 in annotate_highlight
highlighted = highlight(filenode.content, lexer, formatter)
File '.../kallithea-venv/lib/python2.7/site-packages/pygments/__init__.py', line 87 in highlight
return format(lex(code, lexer), formatter, outfile)
File '.../kallithea-venv/lib/python2.7/site-packages/pygments/__init__.py', line 66 in format
formatter.format(tokens, realoutfile)
File '.../kallithea-venv/lib/python2.7/site-packages/pygments/formatter.py', line 95 in format
return self.format_unencoded(tokensource, outfile)
File '.../kallithea-venv/lib/python2.7/site-packages/pygments/formatters/html.py', line 850 in format_unencoded
for t, piece in source:
File '.../kallithea/kallithea/lib/annotate.py', line 168 in _wrap_tablelinenos
for el in self.filenode.annotate))
File '.../kallithea/kallithea/lib/annotate.py', line 167 in <genexpr>
annotate = ''.join((self.annotate_from_changeset(el[2]())
File '.../kallithea/kallithea/lib/vcs/backends/hg/changeset.py', line 273 in get_file_annotate
sha = hex(annotate_data[0].node())