Correct handling when we run out of _get_revision_content() retries.

tasks/afc_statistics.py

@@ -519,9 +519,10 @@ class AFCStatistics(Task):
         try:
             content = res["query"]["pages"].values()[0]["revisions"][0]["*"]
         except KeyError:
-            if tries > 0:
-                sleep(5)
-                return self._get_revision_content(revid, tries=tries - 1)
+            if tries == 0:
+                raise KeyError()
+            sleep(5)
+            return self._get_revision_content(revid, tries=tries - 1)
         self.revision_cache[revid] = content
         return content