Fix double-wrapped exception in capa/inputtypes.py

(accidentally introduced in 07df64eb8c last year)

common/lib/capa/capa/inputtypes.py

@@ -258,7 +258,6 @@ class InputTypeBase(object):
             # Something went wrong: add xml to message, but keep the traceback
             msg = u"Error in xml '{x}': {err} ".format(
                 x=etree.tostring(xml), err=text_type(err))
-            msg = Exception(msg)
             six.reraise(Exception, Exception(msg), sys.exc_info()[2])
 
     @classmethod