[Zope] tal:attributes and semicolon - bug or "feature"?

[Mark Gibson]

This works:

<a tal:attributes="href python:'javascript:alert(\'hi\')'">hi</a>

This doesn't:

<a tal:attributes="href python:'javascript:alert(\'hi;\')'">hi</a>

It looks like tal:attributes may be reading the semicolon as the end 
of the definition, event though it's in a python string.

Is there any explanation other than 'bug'?