Error when reading multiple SimpleMRSs

[goodmami]

This affects pyDelphin v0.4.1.

Parsing a single MRS works:

>>> from delphin.mrs import simplemrs
>>> gen = simplemrs.loads('[ TOP: h0 RELS: < [ "_rain_v_1_rel" LBL: h1 ARG0: e2 ] > HCONS: < h0 qeq h1 > ]')
>>> next(gen)
<Xmrs object (rain) at 140066960825312>

But requesting the next object gives an XmrsDeserializationError, because the final ] was not consumed:

>>> next(gen)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/goodmami/repos/pydelphin/delphin/mrs/simplemrs.py", line 185, in deserialize
    yield _read_mrs(tokens, version, errors)
  File "/home/goodmami/repos/pydelphin/delphin/mrs/simplemrs.py", line 202, in _read_mrs
    _read_literals(tokens, '[')
  File "/home/goodmami/repos/pydelphin/delphin/mrs/simplemrs.py", line 195, in _read_literals
    'Expected \'{}\': {}'.format(tok, ' '.join([tok] + list(tokens)))
delphin._exceptions.XmrsDeserializationError: Expected '[': [

A StopIteration exception is expected for the second next(gen) call.

Also, the exception message is confusing, because it says the expected character is the one received, which isn't true.