Remove attempt at validating feeds in error pages

Also document 403 and web app firewalls for #143

Author: dontcallmedom

docs/error/HttpError.html

@@ -30,6 +30,9 @@ <h2>Explanation</h2>
 <p>This usually means that the URL was wrong, or that permissions on
 the server don't allow us to fetch that file. The error shows the
 message that the server sent, which may help.</p>
+
+<p>If the error is "403 Forbidden" and your Web site uses a Web App Firewall, you may need to allow-list the feedvalidator User-Agent: "FeedValidator/1.3".
+
 </div>
 <h2>Solution</h2>
 <div class="docbody">
@@ -57,4 +60,4 @@ <h2>Not clear?  Disagree?</h2>
 
 
 
-</body></html>
+</body></html>

src/feedvalidator/__init__.py

@@ -215,8 +215,7 @@ def validateURL(url, firstOccurrenceOnly=1, wantRawData=0, groupEvents=0):
           usock = urllib.request.urlopen(request, context=ctx1)
         elif isinstance(x.reason, ssl.SSLCertVerificationError) and "CERTIFICATE_VERIFY_FAILED" in x.reason.reason:
           raise ValidationFailure(logging.HttpsProtocolError({'message': "HTTPs server has incorrect certificate configuration"}))
-        else:
-          raise x
+        raise
       rawdata = usock.read(MAXDATALENGTH)
       if usock.read(1):
         raise ValidationFailure(logging.ValidatorLimit({'limit': 'feed length > ' + str(MAXDATALENGTH) + ' bytes'}))
@@ -238,22 +237,10 @@ def validateURL(url, firstOccurrenceOnly=1, wantRawData=0, groupEvents=0):
     except BadStatusLine as status:
       raise ValidationFailure(logging.HttpError({'status': status.__class__}))
     except ValidationFailure as x:
-      raise x
+      raise
 
     except urllib.error.HTTPError as status:
-      rawdata = status.read()
-      if len(rawdata) < 512 or 'content-encoding' in status.headers:
-        loggedEvents.append(logging.HttpError({'status': status}))
-        usock = status
-      else:
-        rawdata = re.sub(b'<!--.*?-->','',rawdata)
-        lastline = rawdata.strip().split(b'\n')[-1].strip()
-        if sniffPossibleFeed(rawdata.decode('utf-8')):
-          loggedEvents.append(logging.HttpError({'status': status}))
-          loggedEvents.append(logging.HttpErrorWithPossibleFeed({}))
-          usock = status
-        else:
-          raise ValidationFailure(logging.HttpError({'status': status}))
+      raise ValidationFailure(logging.HttpError({'status': status}))
     except urllib.error.URLError as x:
       raise ValidationFailure(logging.HttpError({'status': x.reason}))
     except Timeout as x: