add handling for bad redirects

doab_check/check.py

@@ -36,8 +36,17 @@ class ContentTyper(object):
             r =  requests.get(url, verify=False)
             r.status_code = 511
             return r
-        except:
+        except requests.exceptions.ConnectionError:
+            try:
+                r = requests.get(url, allow_redirects=False, headers=HEADERS)
+                return r
+            except Exception as e:
                 # unexplained error
+                logger.exception(e)
+                return None
+        except Exception as e:
+            # unexplained error
+            logger.exception(e)
             return None
 
     def calc_type(self, url):

doab_check/templates/index.html

@@ -36,9 +36,11 @@ View <a href="{% url 'publishers' %}">the list of publishers whose links we've c
 When a link is checked we record the status code and content type returned by the web server. 
 </p>
 <ul>
+<li>"301" or "302" indicates a bad redirect. 
 <li>"403" indicates a misconfigured server that is not allowing access to the promised resource. 
 <li>"404" means the link is broken - the resource is not found.
-<li>"500" means something has gone wrong.
+<li>"500" means something has gone wrong at the website server.
+<li>"502" means is a gateway error. Some websites use load balancers or content distribution networks; if these gateways have a problem connecting with the sorce website, they send a 502 response.
 <li>"503" means that a website couldn’t be reached. This could happen because the server was too busy, under maintenance, or something else. Amazon's robot blocker returns 503 codes, so these must be checked manually.
 <li>"504" indicates that the server, while acting as a gateway or proxy did not get a response in time from an upstream server. 
 <li>"511" indicates a problem with the security of the connection - most often an incomplete certificate.