daemon: catch RPC_PARSE_ERROR from bitcoind and simply retry

see #238

So far it is unclear why bitcoind sends RPC_PARSE_ERROR, but
instead of doing a full shutdown, let's log the error(+request) and retry.

electrumx/server/daemon.py

@@ -41,10 +41,15 @@ class ServiceRefusedError(Exception):
  some reason.'''
 
 
+class DaemonParseError(Exception):
+ '''Internal - when the daemon returns an RPC_PARSE_ERROR.'''
+
+
 class Daemon:
  '''Handles connections to a daemon at the given URL.'''
 
  RPC_IN_WARMUP = -28
+ RPC_PARSE_ERROR = -32700
 
  id_counter = itertools.count()
 
@@ -172,6 +177,9 @@ def log_error(error):
  except WarmingUpError:
  log_error('starting up checking blocks')
  on_good_message = 'running normally'
+ except DaemonParseError as e:
+ log_error(f"received RPC_PARSE_ERROR ({e=!r}). request was: {data=!r}")
+ on_good_message = 'running normally'
 
  await asyncio.sleep(retry)
  retry = max(min(self.max_retry, retry * 2), self.init_retry)
@@ -184,6 +192,8 @@ def processor(result):
  return result['result']
  if err.get('code') == self.RPC_IN_WARMUP:
  raise WarmingUpError
+ if err.get('code') == self.RPC_PARSE_ERROR:
+ raise DaemonParseError(err)
  raise DaemonError(err)
 
  payload = {'method': method, 'id': next(self.id_counter)}
@@ -201,6 +211,8 @@ def processor(result):
  errs = [item['error'] for item in result if item['error']]
  if any(err.get('code') == self.RPC_IN_WARMUP for err in errs):
  raise WarmingUpError
+ if any(err.get('code') == self.RPC_PARSE_ERROR for err in errs):
+ raise DaemonParseError
  if not errs or replace_errs:
  return [item['result'] for item in result]
  raise DaemonError(errs)