simplify exception handling:

- use WbException throughout, only catch HTTPException from werkzeug routing
- only apply refer redirect check for 404 not found errors
- xmlquery index: log unexpected exceptions, treat missing element as not found

pywb/apps/frontendapp.py

@@ -447,7 +447,7 @@ class FrontEndApp(object):
         :param dict environ: The WSGI environment dictionary for the request
         :param str msg: The error message
         """
-        raise NotFound(response=self.rewriterapp._error_response(environ, NotFoundException(msg)))
+        raise NotFoundException(msg)
 
     def _check_refer_redirect(self, environ):
         """Returns a WbResponse for a HTTP 307 redirection if the HTTP referer header is the same as the HTTP host header
@@ -501,21 +501,29 @@ class FrontEndApp(object):
             environ['pywb.app_prefix'] = environ.get('SCRIPT_NAME', '')
 
             response = endpoint(environ, **args)
-            return response(environ, start_response)
 
-        except HTTPException as e:
+        except HTTPException as hte:
             redir = self._check_refer_redirect(environ)
             if redir:
                 return redir(environ, start_response)
 
-            return e(environ, start_response)
+            response = hte
+
+        except WbException as wbe:
+            if wbe.status_code == 404:
+                redir = self._check_refer_redirect(environ)
+                if redir:
+                    return redir(environ, start_response)
+
+            response = self.rewriterapp.handle_error(environ, wbe)
 
         except Exception as e:
             if self.debug:
                 traceback.print_exc()
 
             response = self.rewriterapp._error_response(environ, WbException('Internal Error: ' + str(e)))
-            return response(environ, start_response)
+
+        return response(environ, start_response)
 
     @classmethod
     def create_app(cls, port):

pywb/warcserver/index/indexsource.py

@@ -250,15 +250,7 @@ class XmlQueryIndexSource(BaseIndexSource):
 
             results = etree.fromstring(response.text)
 
-            items = results.find('results').findall('result')
+            items = results.find('results')
-
-            if matchType == 'exact':
-                cdx_iter = [self.convert_to_cdx(item) for item in items]
-                if closest:
-                    cdx_iter = cdx_sort_closest(closest, cdx_iter, limit=10000)
-
-            else:
-                cdx_iter = self.prefix_query_iter(items)
 
         except Exception:
             if self.logger.getEffectiveLevel() == logging.DEBUG:
@@ -267,6 +259,19 @@ class XmlQueryIndexSource(BaseIndexSource):
 
             raise NotFoundException('url {0} not found'.format(url))
 
+        if not items:
+            raise NotFoundException('url {0} not found'.format(url))
+
+        items = items.findall('result')
+
+        if matchType == 'exact':
+            cdx_iter = [self.convert_to_cdx(item) for item in items]
+            if closest:
+                cdx_iter = cdx_sort_closest(closest, cdx_iter, limit=10000)
+
+        else:
+            cdx_iter = self.prefix_query_iter(items)
+
         return cdx_iter
 
     def prefix_query_iter(self, items):