test-check-py3-compat: don't run py3 part if not build against python3
This test depends on C extensions built for python3, which aren't available
if run-tests.py runs on python2 and no -l/--local is specified.
<tr>
<td class="age">{date|rfc822date}</td>
<td class="author">{author|person}</td>
<td class="description">
<a href="{url|urlescape}rev/{node|short}{sessionvars%urlparameter}">{desc|strip|firstline|escape|nonempty}</a>
{alltags}
</td>
</tr>