convert: workaround for cvsps.cache under Windows
In non-cygwin environment, cvsps fails to create its cache directory and redirect its output to stderr. Just ignore the error and capture stderr as well.
#header#
<title>#repo|escape#: #file|escape# diff</title>
</head>
<body>
<div class="buttons">
<a href="#url#log/#rev#{sessionvars%urlparameter}">changelog</a>
<a href="#url#shortlog/#rev#{sessionvars%urlparameter}">shortlog</a>
<a href="#url#tags{sessionvars%urlparameter}">tags</a>
<a href="#url#rev/#node|short#{sessionvars%urlparameter}">changeset</a>
<a href="#url#file/#node|short#/#file|urlescape#{sessionvars%urlparameter}">file</a>
<a href="#url#log/#node|short#/#file|urlescape#{sessionvars%urlparameter}">revisions</a>
<a href="#url#annotate/#node|short#/#file|urlescape#{sessionvars%urlparameter}">annotate</a>
<a href="#url#raw-diff/#node|short#/#file|urlescape#">raw</a>
</div>
<h2>#file|escape#</h2>
<table id="filediffEntry">
<tr>
<th class="revision">revision #rev#:</th>
<td class="revision"><a href="#url#rev/#node|short#{sessionvars%urlparameter}">#node|short#</a></td>
</tr>
#parent%filediffparent#
#child%filediffchild#
</table>
<div id="fileDiff">
#diff#
</div>
#footer#