[migration] re-try without print_function when compiling a script fails
As part of the python3 porting we added the __future__.print_function import to
cubicweb.migration. That started affecting all migration scripts it runs,
which may not be prepared. So if compiling a script results in SyntaxError,
try again without the print_function flag.
Closes #7935030
<html>
<head>
<!-- dependencies -->
<script type="text/javascript" src="../../data/jquery.js"></script>
<script src="../../data/cubicweb.python.js" type="text/javascript"></script>
<script src="../../data/cubicweb.js" type="text/javascript"></script>
<script src="../../data/cubicweb.compat.js" type="text/javascript"></script>
<script src="../../data/cubicweb.htmlhelpers.js" type="text/javascript"></script>
<!-- qunit files -->
<script type="text/javascript" src="../../../devtools/data/qunit.js"></script>
<link rel="stylesheet" type="text/css" media="all" href="../../../devtools/data/qunit.css" />
<!-- test suite -->
<script src="cwmock.js" type="text/javascript"></script>
<script src="test_htmlhelpers.js" type="text/javascript"></script>
</head>
<body>
<div id="main"> </div>
<h1 id="qunit-header">cubicweb.htmlhelpers.js functions tests</h1>
<h2 id="qunit-banner"></h2>
<ol id="qunit-tests">
</body>
</html>