Catch Harmony difficulty exception (#24)

Author: namikmesic

src/collectors/bitcoin.py

@@ -29,7 +29,7 @@ async def _probe(self) -> results:
                 results.record_block_height(self.url, chain_info['headers'])
                 results.record_total_difficulty(self.url, chain_info['difficulty'])
         except Exception as exc:
-            logger.error("Failed probing {} with error: {}".format(strip_url(self.url), exc))
+            logger.error("Failed probing {} with error: {} of type: {}".format(strip_url(self.url), exc, type(exc)))
             results.record_health(self.url, False)
 
     def probe(self):

src/collectors/evm.py

@@ -44,7 +44,7 @@ def probe(self) -> results:
                     if self.record_difficulty:
                         results.record_total_difficulty(self.url, self.client.eth.get_block('latest')['totalDifficulty'])
                         results.record_difficulty(self.url, self.client.eth.get_block('latest')['difficulty'])
-                except ExtraDataLengthError:
+                except (ExtraDataLengthError, KeyError):
                     logger.info("It looks like this is a POA chain, and does not use difficulty anymore. Collector will ignore difficulty metric from this point on.")
                     self.record_difficulty = False
                 try: