CLN: replace %s syntax with .format in pandas.io (#24719)

progress towards #16130

Author: makeajourney

pandas/io/packers.py

@@ -519,7 +519,8 @@ def encode(obj):
  elif isinstance(obj, date):
  return {u'typ': u'date',
  u'data': u(obj.isoformat())}
- raise Exception("cannot encode this datetimelike object: %s" % obj)
+ raise Exception(
+ "cannot encode this datetimelike object: {obj}".format(obj=obj))
  elif isinstance(obj, Period):
  return {u'typ': u'period',
  u'ordinal': obj.ordinal,