Fragment in PermissionError msg results in TypeError

[Ryan J Ollos]

>>> from genshi.builder import tag
>>> from trac.core import TracError
>>> from trac.perm import PermissionError
>>> from trac.util.translation import tag_
>>> from trac.util.text import to_unicode
>>> e1 = TracError(tag_("This is a %(fragment)s", fragment=tag.em("Fragment")))
>>> to_unicode(e1)
u'This is a <em>Fragment</em>'
>>> e2 = PermissionError(msg=tag_("This is a %(fragment)s", fragment=tag.em("Fragment")))
>>> to_unicode(e2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "trac/util/text.py", line 74, in to_unicode
    return unicode(text)
TypeError: coercing to Unicode: need string or buffer, LazyProxy found

The following patch seems to fix the issue, but I am unsure that it is the correct solution.

trac/perm.py

@@ -59 +59 @@
                          'operation. You don\'t have the required '
                          'permissions.', perm=self.action)
         elif self.msg:
-            return self.msg
+            return unicode(self.msg)
         else:
             return _('Insufficient privileges to perform this operation.')