ENH: check badips.com response on presence of "categories" in it

As https://travis-ci.org/fail2ban/fail2ban/jobs/50609529 query might fail in
that response would not contain "categories".  With this change we will handle
it explicitly and will spit out ValueError, providing information about
the response so it could be troubleshooted

config/action.d/badips.py

@@ -111,6 +111,8 @@ class BadIPsAction(ActionBase):
 		------
 		HTTPError
 			Any issues with badips.com request.
+		ValueError
+			If badips.com response didn't contain necessary information
 		"""
 		try:
 			response = urlopen(
@@ -122,7 +124,13 @@ class BadIPsAction(ActionBase):
 				messages['err'])
 			raise
 		else:
-			categories = json.loads(response.read().decode('utf-8'))['categories']
+			response_json = json.loads(response.read().decode('utf-8'))
+			if not 'categories' in response_json:
+				err = "badips.com response lacked categories specification. Response was: %s" \
+				  % (response_json,)
+				self._logSys.error(err)
+				raise ValueError(err)
+			categories = response_json['categories']
 			categories_names = set(
 				value['Name'] for value in categories)
 			if incParents: