Merge #18633: test: Properly raise FailedToStartError when rpc shutdown before warmup finished (take 2)

fa03713 test: Properly raise FailedToStartError when rpc shutdown before warmup finished (take 2) (MarcoFalke)

Pull request description:

  actually (?) fix #18561

  See most recent traceback https://travis-ci.org/github/bitcoin/bitcoin/jobs/674668692#L7062

  I believe the reason the error is still there is that ConnectionResetError is derived from OSError:

  ConnectionResetError(ConnectionError(OSError))

  And IOError is an alias for OSError since python 3.3, see https://docs.python.org/3/library/exceptions.html#IOError

  So fix that by renaming IOError to the alias OSError and move the less specific catch clause down a few lines.

ACKs for top commit:
  jonatack:
    ACK fa03713

Tree-SHA512: 6e5b214ed9101bf8ebe7472dcc1f9e9d128e2575c93ec00c8d0774ae1a9b52a8c2a653a45a0eab8d881570b08dd5ffeddf5aca88a10438c366e1f633253cb0b5

Author: MarcoFalke

test/functional/test_framework/test_node.py

@@ -225,9 +225,6 @@ def wait_for_rpc_connection(self):
                 self.rpc_connected = True
                 self.url = self.rpc.url
                 return
-            except IOError as e:
-                if e.errno != errno.ECONNREFUSED:  # Port not yet open?
-                    raise  # unknown IO error
             except JSONRPCException as e:  # Initialization phase
                 # -28 RPC in warmup
                 # -342 Service unavailable, RPC server started but is shutting down due to error
@@ -237,6 +234,9 @@ def wait_for_rpc_connection(self):
                 # This might happen when the RPC server is in warmup, but shut down before the call to getblockcount
                 # succeeds. Try again to properly raise the FailedToStartError
                 pass
+            except OSError as e:
+                if e.errno != errno.ECONNREFUSED:  # Port not yet open?
+                    raise  # unknown OS error
             except ValueError as e:  # cookie file not found and no rpcuser or rpcassword. bitcoind still starting
                 if "No RPC credentials" not in str(e):
                     raise